Why is a person who plays the piano called a pianist but a person who drives a race car not called a racist?

I don't know, why don't they call him a carist. This can go on forever, What is the motive behind the question?

It was hypothetical. A muse {note the winking eye} But still I enjoyed your answer.

Ahh the joys of the English language.
You probably know this being a Dad but young children will make up new words following the rules they have learnt from other words. That's why they say things like writed rather than wrote.

It's a mystery to me as well

Because racist has another meaning... loved your signature though

Racist has another meaning but so does "which" and "witch".. The english language is not a spiritual one either.. I mean why would you want to greet someone by saying HELL-o.. you I know Hell is low and heaven above but come on, it's a greeting.. so I choose to say High instead. There is already enough negative connotations associated with a black male, did there have to be a word "blackmail" to make things worse? I could go on.. I have changed my vocabulary and I am now use to it.. some think I'm weird but hey..