Lots of people do. It's just like putting a cave in. gives a territory and lots of africans like to have their own cave. I like one cave per fish in each tank. Be it rocks or flower pots or the combination of each. Mainly use flower pots in breeding tanks and rock caves in my show tanks.
I have them in my breeder tank. In my display tanks I do not use them. They don't look natural to me. Then again, I will never do a bare bottom tank except for breeding tanks either. To me the aquascaping is as important as the fish....