So apparently, when I was lying in bed last night, I thought of this.
Another advantage to “incentives” is that they give “permission” to people to do things they might not otherwise do. I think this is sortof similar to how rules and dice allow the GM to say “It wasn’t me who made that bad thing happen, it was the dice!” having incentives allows players to say “I did it for the XP!” and for people to understand that, yes, that’s kinda the point of the game. The game is clearly telling you to do that thing. So you don’t need to apologize for doing it.
This does mean that you need to be really kinda careful with what kind of behaviors your system incentivizes (See: Murder Hobo) but it’s possibly the most powerful thing about incentives.