The reason why we have Romero (and Grant) as our backup is that he's capable to step up when needed. I don't see a reason why we can't start him, especially when the main goalkeeper is in such a bad form (or decline). Fergie dropped de Gea on multiple occassions and I don't think Lindegaard back then was a much more reliable option compared to Romero.Well because he doesn't have any other alternatives, unless suddenly he starts trusting Romero to play every game.
People said same thing about Lingard, Pereira, once Bruno was signed Lingard barely makes first team squad. When you have good squad, you can drop any player. When your depth is so shit that one injury means Lingard or Pereira will play, then he can't drop anyone.