Are tight pants meant to be wore under other workout pants or alone?

I depends on the type I supposed. Tight ones like running pants can be worn alone. Sometimes people wear them under running shorts for some warmth and cover though.

alone, I think

If they're the super tight ones, I wear shorts over them, to keep from it making it look like my butt got hungry.  
But I think they can be worn alone and look decent on the right person.