Yes. YOU! You, sitting there, reading this post. You, my favorite follower.
When writing anything, fantasy or otherwise, you are bound to put a lot of yourself into your world. Seriously. Think about it.
What sort of world would you create? What customs and cultures do you find yourself drawn to? What sort of climates would there be? Would you have everyone on equal footing or would you have people struggling in the streets?
Well, a lot of that in world building is going to be necessary. Humans were given the gift of free will, after all, so you may have those beggars in the streets. Your world will take on a life of its own, of course, but it would be interesting to see what you'd put into a world of your own creation. If it is Sci-Fi, I bet you would have lots of cool gadgets to make life easier, simpler.
You put just as much of what YOU want into your world, just like you put parts of yourself into characters. There will be traces of your personality everywhere in your characters and your world.