When I was starting out, I did not do short fiction well, because I kept wanting to write books.

Empress of the Universe would be way too much work. I'd have to wear fancy clothes, probably including lady shoes with pointed toes, and could no longer slouch into the study in PJs and slippers. Someone would (avert!) straighten my desk. Someone would reorganize my yarn stash...in fact, they'd assign someone else to knit my socks, thus depriving me of an excuse to rest my brain while pretending to accomplish something useful.

Other people, including me, have written books with main characters who were old and rich. Or old and brilliant. Old sages, old wizards, old rich people.

I revear all the gods but those that delight in cruelty. If Ra's light is kindly in your eyes than may his light shine on us all.

You can also make explicit certain social problems which, again, would be prejudged or not encountered at all in real life, because people have set up defenses against it. Fantasy allows you to get past defenses.

I love biomedical science, I love astronomy, and you can't really do much with those in a fantasy setting.

My first degree came years before my second. I had wanted to be a physicist, but I flunked calculus.