Writing is a communication.
There are a lot of people who write very intensely about things they do not and cannot do.
Inner space is so much more interesting, because outer space is so empty.
Some major writers have a huge impact, like Ayn Rand, who to my mind is a lousy fiction writer because her writing has no compassion and virtually no humor. She has a philosophical and economical message that she is passing off as fiction, but it really isn't fiction at all.
In science fiction, you can also test out your own realities.
For years, I thought I simply didn't dream. I felt left out. Everybody else had a thing I didn't have.