Why is it that wind bands often have a string bass in them? It seems somewhat pointless to me to have a string bass when there's no way it will be heard over several tubas. Does someone know about the history and purpose of including a string bass in a wind band?

From the Contra Costa Wind Symphony (http://ccwindsymphony.org/WhatIs.htm)site:
"Many wind bands have retained the string bass in their midst, to assist in delicate passages which tubas sometimes seem to clumsy in."

I was the string bass player in the Oklahoma State Wind Ensemble while I was there, and I asked the director the same question. Mainly because everyone was asking me that question. He gave pretty much the same answer as above.

They also help with the overall balance of the band, i.e. if you
have a piano marked and you can't hear the bass, you're too loud.