Why use the key of C#?

Question

I was reading about Brahms, and it was mentioned that he had composed a piece in C# Major. AFAIK, we generally don't use C# Major in jazz or rock music because the key signature has 7 sharps, so it's easier to use its enharmonic key - Db, which only has 5 flats in its key signature. Why would a classical composer like Brahms compose something in C#?

Answer 1

For one thing, stringed instrument players prefer to read sharps in a piece of music over reading flats. They prefer to play in sharp keys, as a result. C# being a sharp key would be preferable for string players in an orchestral or chamber work.

Also, if the piece modulates to the parallel minor i.e. C#-minor, it would be easier to notate than were one to begin in Db-major and modulate to Db-minor, which would not be common.