I started learning to read bass clef about 3 years ago, after playing for about 20 years before that.
I wish I had done it earlier. I'm no longer limited to what I can find with tab, or endlessly repeating CDs to work something out. It also opens up music for other bass freq instruments like the piano and some cello where there just isn't any tab.
It also means that when my kids bring music home (sax and clarinet) I can play the accompanist part.
It's not necessary to learn to read to play bass, but I think it is clear that in any subject having more information and knowledge is always a good thing.