maybe because he can't get a game, though to be fair, he's only 18. but i think it's fair to say he has professionalism issues, and that lack of professionalism was not the reason why either of bergkamp, henry and vieira didn't set the world alight while at inter, juve and milan (those clubs are also a small step up from levante).
those guys got it, fabregas got it, wilshere got it, miyaichi seems to get it (not saying he's in the same league in terms of talent). wellington doesnt get it. you can say his behaviour is typical for 18 yr olds, but that's precisely the point - a typical teenager isnt expected to become a top class footballer earning millions.