I look from the perspective of a player and think to myself; why would a player want to look for the training room first, before a duel room with 1 player in it, where he can duel? There's no real reason one way or the other, except that in the opposite question more people would probably be looking for the duel room than the training one. In an ideal world, I would imagine the first page containing at least 1 room from each category of play, but sadly due to the high number of categories this doesn't seem trivial to implement, while just moving training rooms and quest to the end is.