As a matter of fact, for the past few jamming sessions my band has lacked a bassist. And the result is that it just doesn't feel complete. Something vital is missing from the music. Which is why since I can play a bit of bass, I usually fill in as bassist for some songs.
So yeah, there you go. Even bands like 30 Seconds to Mars that lack a permanent bassist, they have a session bassist record tracks for them, and they have a live bassist to play live though these are on a temporary basis. The simple truth about rock and metal music, is that there are three important parts - the guitar, the bass and the drums. Without one or more of these, something is wrong.
Of course I am excluding acoustic rock, acoustic stuff, but even these usually have an instrument handling bass to some extent, not necessarily a bass guitar.