There’s also the idea that since the system “works” it shouldn’t be changed. IIRC Le Guin did some stories on a place called Omelas that explored a similar idea: there’s this utopian city, but they chuck a child down a hole to suffer there, which for some arcane reasons is deemed as necessary. Once people learn of this, they either accept it as indeed necessary or (rarely) leave.

A utopia only works if everyone thinks of the same thing as being a utopian society, which people generally just don’t.