Shift work makes it difficult. If others in the band aren't working shifts then nobody wants a bassist who can only rehearse alternate weeks. If others in the band are shift workers then usually the shifts don't coincide so there's no rehearsals at all. "What about weekend rehearsals," I hear you cry. I'd be up for that too, but nobody likes rehearsing at the weekend for a number of reasons - the day they have the kids, the missus wants to go shopping, it's my day in the pub, the football is on, can't be arsed etc etc.
So I have to wait for quiet periods when shifts stop and I work regular days... then shifts come back and I ask to stay on days... which is ok for a few weeks then I get the threats about what will happen if I don't start doing shifts again, and bye bye band.