Kinda curious now, what was the reason the AoO was denied?

In actuality? Because he doesn't attack.
But, if I were to make up a rules reasons, it would be a stance or some such, otherwise it wouldn't call for a martial lore roll.

There are plenty of maneuvers that allow the initiator to move without triggering an AoO, even in 3.5e.

I'll admit to not really being familiar with maneuvers in general. I usually play spellcasters, and none of the more hands-on types in any of the games I've played ever mentioned them.

There are some fights you can't win, and some fights that are not worth winning.

Share a time when someone retreated from a fight, and made sure everyone know that they were not running away.

Defeated demon on the other side of the street.
Demon wakes up, and for some reason everyone runs TOWARDS the demon to investigate.
Except the sniper, who was supposed to be the bravest one of the groop.
He said: "Why would you even want to go out there? I'm NOT walking out of that door, no way. That demon is going to wreck us if he survived our first beating!" Pauses, and says as an aftertought to the GM: "Umm, is it possible to get to the roof of this building? Because it was totally my plan to snipe him from a distant all this time, my character is totally not afraid or anything. Just making sure to have distant so I can shoot it, okay?"

During the various climatic one-on-one fights of our Weapons of the Gods campaign, me and my opponent were duking it out in the desert, each of us down to our last dregs of strength. I proceeded to...well...run. My Kung Fu included a lot of movement bonuses and so with one action I placed a healthy distance between us and then stopped.

'40 Feet. This distance is all I need to defeat you,' I had my character declare. 'This is your last chance to give up.'

Naturally, my opponent didn't heed this warning and began to cover ground to reach me. Now, it's worth noting I'd already learned he didn't have any movement bonuses in his Kung Fu, so what I covered in one action took him about three. In WoGs the big thing all your abilities, especially Kung Fu, rely on is Chi. You spend chi to use Kung Fu, and you gain a small amount back each turn. However, you can take a 'breath' action to restore more Chi. The three turns he spent covering ground gave me all the room I needed to restore enough Chi to unleash my strongest combination of techniques one more time.

Sure enough, he reached me and attacked, tearing out another chunk of my health, but my turn then hit and I was able to completely obliterate the last of his health (and turn a swathe of sand into glass, but when you use a lot of fire and light infused Kung Fu, this stuff happens.)

I was playing a LE Half-Orc Monk named Blundah. Our Fighter decided to antagonize a really big (Gargantuan or Colossal, not sure which) dragon by smugly claiming to be smarter than it (he wasn't), recited some stupid 'riddle' that just insulted it (greeeaaaat) and proceeded to make demands...

So its planning to eat everyone. I know someone gon' die if we fight that thing... and I win initiative. We were in a massive dungeon room with lots of twisty passages around. So.. I did the only thing that made sense.

Lure it away.

"OY! Y'OVERGROWN NEWT!"

*Most of party winces*

"Y'really think yer all unbea'able an' tripe? See if y'kin keep up wif me."

*Le run-the-fuck-down-a-narrow-hallway as fast as my monk legs will carry me. It ignores me*

As the party proceeds to try to not-die, I attack it's pride by claiming to understand why it doen't wanna race me. After all, it's kin weren't too fast neither, and I show off my dragon-tooth punching bracers.

...

Okay NOW it's chasing me. As I bolt through the passages, the DM takes a smoke break to figure out the Dragon's tunneling speed.

I wasn't running away, I was racing! I managed to effectively trick the dragon into repeatedly running into danger (set up by the party) until it was weak enough for us to handle.

In my case, the running away was most certainly necessary. It was the end of the fourth book of Carrion Crown, the "HP Lovecraft" arc of the campaign. We were in an underwater temple that had been taken over by Mi-Go, and our paladin accidentally completed the ritual they were using to summon a spawn of the local Shub-Niggurath expy.

So while we were panicking and giving Sir Ahsum a hard time over that, I got a brilliant (but stupidly reckless) idea to get rid of the spawn and destroy the temple at the same time. So Chekyl, my tengu alchemist, set up the Mi-Go's machinery to explosively overload, and we all ran back to the entrance as hard as we could.

Thankfully, the gods were with us, and we just barely managed to escape to our submersible in what was one of the most nail-biting scenarios in the entire campaign.

Oh, just to clarify, we didn't have to outrun the explosion itself. Blowing up the machinery ruptured the ceiling, and since it's an UNDERWATER temple, we had to outrun the flood of water that came rushing in.

On top of that, we still had the spawn chasing after us, though it ended up caught up in the flood more than we were, and taking constant damage from it. There were a few Mi-Go that we had missed because they were in an offshoot path that we hadn't explored, too, and they tried to slow us down. With a little teamwork and a lot of luck, though, we were just barely able to make it out before the place flooded completely.

Ah yes, the skill nobody puts ranks in because martial adepts are so fond of calling out their attacks.

And because maneuvers are far less likely than spells to allow effective methods of response, other than the usual anti-melee stuff.

And because there isn't a single prestige class which requires ranks in it.

...Why does this skill exist again?

Yes, Phil vs Chu! This is definitely a match I want to see!

You know, I'm also looking forward to Phil vs. Chu... but I don't want it to follow the same vein that Usopp vs Chu took, as in Usopp finally overcoming his cowardice to risk his life for a nakama.

Me, I actually more see it as Phil earning his stripes at the gaming table. GM starts it off saying, "You know, I made this character to fight Luffy. I know what Usopp can do, and he'd stand no chance against Chu, so I'm going to have Chu walk away thinking that Usopp is dead. So, just stay down and you can join up with everyone later."

And we all know what the concern and kindness of a GM does to Gamer competitiveness. Especially if he had a hammer that dealt minuscule damage with a one round stun effect... /trollface

Fishmen get fast healing in water, and I believe Chu ended up in a paddy or something at the end of the fight before the repeated hammer blows, so I reckon the hammer will end up being Phil struggling to do more damage than the fast healing