You don't "have to have" anything. Do you want one? Do the scenarios you find yourself in would benefit from having a B string?
For me, the answer was "yes" for a while, then became "no" later on. I have kept my 5 string because sometimes it can be useful (I occasionally play with a singer who often sings in Ab or Eb) but I mostly went back to a 4 string. Your situation might be different, only you know what you need.
For me, the answer was "yes" for a while, then became "no" later on. I have kept my 5 string because sometimes it can be useful (I occasionally play with a singer who often sings in Ab or Eb) but I mostly went back to a 4 string. Your situation might be different, only you know what you need.