probably because the opponents you have in adventure mode aren't usuall classes like Warrior, Rogue etc. so you would have to add the game type "adventure" and the different bosses as "classes" into the routine to make it work if some1 is good in programming he could work something out, but i think it's bit hard because it's not just simply adding 20 lines but i look forward to future support of this game mode by the bot (as i'm sure their will be more adventures in the future)
I hope some one do. Just bought all of the naxx in normal but I dont play the game - only the bot does so I have no idea how to do this ;-) and I cba try