I suppose those that don't have adequate control over something like that happening probably do.
However well maintained my basses are, something going wrong is ultimately out of my control, why risk it?
My band's live setup is pretty complex, with dmx triggered lighting shows, midi triggered patch changes, backing tracks, IEMs, clicks, the works. It's all run off one rack and effectively a macbook, and we are far from being able to afford to have a backup rig. If the macbook dies on the day, we can't gig. It TERRIFIES me, so I like to control what I can control wherever I can.