It depends on what you want to do with music. If you're only musical ambition is to be in a punk band playing root notes, then knowing music theory probably won't matter. If you want to be a musician and not "just a bass player" then absolutely, music theory is vital. Music is a craft, just like being a carpenter is a craft. Would you hire a guy to add a room to your house whose only experience was tinkering with wood for fun in his garage on the weekends? He might be able to make a really nifty chair or birdhouse, but the more complicated stuff would probably be beyond his skill level. Music is a craft, musicians are craftsman. It takes a while to reach that level of expertise, but it will separate you from the mere hobbyists...not that there's anything wrong with being a hobbyist if that's all you want to do.