I wrote for years purely for instruments, before I actually became a 'songwriter' (e.g. writing lyrics to my melodies). Looking back, almost my whole instrumental catalogue, except for one wild piece for instruments and narrator, is singable. It has to do with being around Broadway, theater, and GASB music that was around my house from early childhood. As a consequence, everything I've written in a jazz or even pop idiom is singable and lyric-ready.
So, yes, to a large degree. I'd like to challenge myself and write some non-melodic stuff at some point in the interest of growth. Even the great Sondheim studied with serialist Milton Babbit.