pgt: another reason is that on this site (different than on other sites) the new dice are rolled when the player views the game. So when you are on the bar and your opponent makes a move, the site doesnt know what you will roll in the future (as you are not viewing the game yet), yo might escape when you roll well, you might not when you are unlucky (or didnt bribe enough ;)).
Autopass cant be implemented for those case.

There are however situations that you will have to pass regardless your rolls (for example when you are on the bar, and the whole home is blocked), in those cases autopass might be partially implemented.

i asked fencer about that in a game we had and he said he would think about it and might implement the partial autopass ... he doesnt know when though

(at least its better than the 'no' we usually get about plain autopass ;))