Do you "have to" know how to use open strings as part of the patterns on the bass? Of course; it's fundamental understanding of your instrument. But that said, in practice, almost the only open note I ever play is E.
Certain drone/octave parts might utilize an open string sometimes, and you can sometimes use an open string passing note to allow for a big left hand shift. But other than those reasons, or hitting the low E that is so often needed, I don't find it advantageous to use open strings on a bass guitar.
You have easier control over the character of your notes if you are fingering them, rather than playing them open. I usually play right on the frets (or just slightly behind them), use a lot of barring, and do a ton of subtle tonal and note control using my left hand (usually without even realizing it), based on small variations in where exactly I finger in relation to the fret, how hard I press, how I roll or lift or tap my fingertips to control the decay of notes, etc. Take that away by incorporating lots of open strings, and I realize how much I am doing with my left hand, without even realizing I'm doing it. The instrument starts to feel a bit clumsy to me. When I do use open strings, I find myself fingering them at the nut anyhow, to give me the same tonal and muting control I have in any other position.