Another reason is that actual utopias make for pretty boring writing. Humanity convinced itself that they lived in a perfect world, but most of the writing was

Another reason is that actual utopias make for pretty boring writing. Humanity convinced itself that they lived in a perfect world, but most of the writing was about the cracks in that facade. Even the preachy and awful first season of TNG had the character of Q demonstrating that we still had a long way to go.