i dont think every trainer gets the starters, i think its more tied to the fact that we are on an assignment from the professor to fill the pokedex, whereas most other trainers start their journey in their own hometowns, possibly after being given a pokemon from a friend.
i dont really want three potential mega evolutions to be taken up by the monkeys though. i get the impression that they are intended to be a supplement to the starter, just not as good, so they are only used for ingame. although that pseudo-starter role may also why they actually have a chance of mega evolving. if having them doesnt cause fewer other pokemon to get megas then i would be fine with it though.
but we already have a gen 6 pokemon with a mega announced, so i dont know that the generation difference is the biggest factor, although diancie may be a special case, with its whole rock theme, steven stone being in the next game, and mega evolution being tied to rocks. maybe diancie is specifically tied into mega evolution and therefore an exception? --- FC: 2122-6099-9489 IGN: Evan