In other words, double standards.
Had Amauri played, he might've created a chance, maybe even two on his own because of moving around more, holding the ball up top. If he had missed those two, people would be all over him saying 'ahh he needs 10 chances to score a goal, he's shit, Trez would've scored those'.
I love Trez, but in a team that's clearly not a finished product yet he's not likely to get that many great balls, so Amauri is a more useful striker at this point.
I agree that people moan too much about Trez not getting involved though, that's the kind of player he is. We all know he can deliver.