The pulp writers of the thirties and forties on up to the fifties did this. They jumped from one genre to another. The main three that they would focus on would be crime fiction, horror, sci fi. Today's writer's do the same thing-- and alot of them mix genres, such as western horror, sci fi horror etc.
It is easy to understand why as writers we do this. I for one, get this surge that I affectionately call "the writing bug" where all sorts of story ideas come to me in just about every genre. As a result, I just want to write it all. But, with all this in mind I am left with a question, should you write an all sorts of story categories, or should you stick to just one or two? Of course there are many opinions about this.
Right now, I am happy to continue writing clown flavored crime fiction and to keep honing my western chops.