In music, the bare minimum is usually piano and drums, but if you're doing something "a cappella", you can have just drums or nothing. Everything else is flavor. Bass, horns, strings, guitar...they're extra. If the bass is playing with piano, usually they work together, but if you're in a band that's formed around the pianist then, depending on how they play, you might just hold the root and never get to "shine", which is what I think this whole discussion is about. We all like to have room to be free, and if everyone is being "free" then it'll sound messy (at least to some people, "Free Jazz" comes to mind). In Jazz and Classical music, usually they play around with the instruments. Gospel isn't that complex, at least not yet. Gospel is "mainly" about the words.