Well, it's more complicated than that. Bounty isn't tied to pirates, even with them disabled you can put bounty on players and it can be collected by destroying units of that player. It's just that in a 1v1, there's no point to use it because you can't collect bounty that you put up. It's always been said that the AIs were not really "optimized" for 1v1 play, so they still try to use the bounty system like they would if it was a multiple-player game.

At first you could, but they took it out at some point (presumably to prevent exploiting of the techs that vary the amount of reward/cost to place to make credits?).  I think you still are not able to.