I spent a summer working on a cruise ship about 6 years ago. In my experience I had to be an excellent sight reader. The singer just called out page numbers from two books of songs, you just turned to that song and played it. It was all standard notation, no chords. There was never any rehearsal, simply because there was nowhere on the ship to rehearse. There was a real mix of genres, one night was cocktail night, so that was jazz, the only exception to reading standard notation, that was just following lead sheets.
I did an honours degree in music, graduating last summer. We were encouraged to adopt a portfolio approach to working. So as well as playing, I teach a lot, (I have a Rock school teaching qualification that I did as part of my final year). A friend of mine who's an amazing player, also writes in Bass guitar magazine. I write music and earn a little from that. I did some for an advert earlier this week.
Being able to fluently and accurately play a whole mix of styles is important, i.e. being able to a jazz gig one night, improvising off lead sheets, then the following playing standard function tunes, some of the dep gigs that I've done again require turning up and sight-reading charts. I'm doing panto in January for a couple of weeks, again sight-reading.