The biggest reason i play at AG are games with quests. It passed lots of months and no new game with quest have been added? Why? Is it hard to put some quests to random games? This is the best gaming site i know!
I don't know why, but I can imagine a possible reason, although there are almost certainly other factors. As far as I know adding quests to a game requires the participation of the game dev(s), in order for the site to recognize when you have fulfilled certain criteria within the game. Maybe there haven't been any good occasions in a while?
Another reason might be the transition to HTML5. Armor Games' system supports quests for HTML based games now, but maybe it is more difficult for game devs to add quests in HTML than it was in Flash? This is pure speculation on my part, but who knows.
I know it's a bit late, but most of the threads here have gone a bit without a response.
As a programmer/studying game developer I can say that HahiHa is spot on. Without the dev's participation in the matter it would be practically impossible to add quests, and even if they could, I could foresee potential legal problems if they were to go and add quests without at least the dev's express approval.
As for the other reason he mentioned, it's been a while since I heard, but last I heard he is correct; quests are only supported in Flash at the moment.