Not every person has 4 hours a day to hunt for a epic pokemon. (A +25 important stats + 20 other stats, good nature, good ability) This can even take weeks.
Roleplay? On Anime you need a strong bond to Mega Evolve, or Ash Charizard can Mega Evolve with Damian ( the kid who abandoned charmander)? No, and if we measure it with happiness everytime your pokemon dies he losses happiness. And it is almost impossible for pvp players to have their pokemon with high happiness. By the way you loss 5 points when your pokemon faints and only 1 when your pokemon kills other Pokemon.
So based on the "roleplay" of Anime the OT doesnt has sense. And putting it on the happiness idea that would just take out Megas of pvp.