Let me put it this way:
I generally don't flag since I don't want to be subservient to the person I'm flagging to. And that's what flagging is: bowing to the guy in first, begging him to protect you so you get some of his glory.

I'd rather keep fighting and come in 3rd or 4th than flag for a protected 2nd.

This is not to say I won't ally: I'm fine with making truces, and respecting them to the end of the game. But I won't flag it.

A lame scenario: The two people with the largest land and the highest dice trucing in order to beat everyone else. That's fine, though annoying, if they want an epic showdown between each other. It's lame if one of them flagged to the other to say, hey, you're the boss.

That was the difference. I'll flag to leave the match if I think I can't win, and I don't want to go through the gameplay. It's not complicated.