Probably because you threw up KDB and Salah as justifications for sticking with youth players who aren't the finished product despite the overwhelming pattern of odds suggesting players are far more likely to turn into a McAleny than a Salah.Again, I'm not saying play a team of academy players. Fear I'm not really being understood here.
It's easy to point to the few times when letting players go has been something clubs can regret as they're much more memorable than those who don't but they're far outnumbered by the amount of players who never kicked on and we're rightly let go. It's a law of averages.