Against foes without Combat Reflexes (i.e. virtually anybody), it may be useful for a tank or character with Mobility to provoke an AoO in order to make the AoO unavailable against a more vulnerable character later in the round. I had a monk who once helped a cleric who was out of turning attempts and had a pathetic Concentration score Cure the snot out of a nasty undead ... Kind of freaked out the DM.
Me: "I move past and flank it."
DM: "OK. Make your Tumble roll."
Me: "Nah. I don't think I'll tumble today."
DM: (pause) "Oh ... I see what you're trying to do."
Me: "I'm sure you do. But does it?"
DM: (Pause, sigh) "What's your touch AC?"
Me: "Against the attack of opportunity? 23."
DM: (grumble)
Me: "I move past and flank it."
DM: "OK. Make your Tumble roll."
Me: "Nah. I don't think I'll tumble today."
DM: (pause) "Oh ... I see what you're trying to do."
Me: "I'm sure you do. But does it?"
DM: (Pause, sigh) "What's your touch AC?"
Me: "Against the attack of opportunity? 23."
DM: (grumble)