This should be a simple concept: if it's your music and your money, you can play whatever bass (or basses!) you like. If someone else is paying, you are an employee, and you should be prepared to meet your employer's expectations. 99% of the time, this means showing up with a flexible attitude and a few standard bass options: a P-Bass, plus Plans B and C (Jazz, Stingray, flats, fretless, etc.). If your genre calls for a five-string (Modern Country, Gospel, etc.), bring one of those.
There's nothing wrong with loving the sound of your hand-carved, Cocobolo-topped six-string, with elf-wound 27-volt Unobtainium active pickups, and fretboard wood salvaged from the deck of the HMS Intrepid. Heck, if it doesn't slow down your load-in (or crowd the room...), bring it, too! There's nothing wrong with having a Plan D.
Now, if you're Bernard Edwards and they want your magic funk, show up with nothing but a Stingray, flats, and a cool hat. If you're Geddy Lee, and they want you to come in and do a "Geddy Lee" on the track, then by all means, bring your Jazz, Ric, and SansAmp and have at it. But, most of us aren't Bernard Edwards or Geddy Lee...
Absolutely agree with this, especially the 1st paragraph.
I recall 2 interviews of 2 very good bassists. One was Chris Squire and one was Victor Wooten. Both talked briefly in their respective interviews about not getting session gigs.
Chris Squire because of what he played and how he played it; Ric with a pic.
Victor Wooten because of how he's perceived as the virtuoso soloist and nothing else.
My bass instructor has been around with a certain band since the early 80's with major and indie record contracts and also plays in at least 6 local bands ranging from hard rock to prog to Jazz to Funk to Avant Garde. He does session work at local recording studios as a gun for higher for other bands and commercial jingles, does work for local theatres for various musicals, teaches bass (electric and upright) and piano, co-hosts an open mic with a guitarist and a drummer and plays church organ at a large church where he has the gig for all the masses, including Sundays, holy days, weddings, funerals, etc. He makes his living from music and nothing else.
He uses 3 different P basses, an Upright, a Jazz, a Ric and a 5 String Pedulla The Jazz and Ric are primarily for the Rush cover band he's in. The Pedulla is used for the Avant Garde band he's in as well as one of the P-Basses.
For session work and all the other bands he's in he is playing one of the P-Basses. The major band that he's in he now plays mostly Upright Bass.
When he does session work he demands getting paid per song rather than by the hour as he usually does his job in one or two takes. He's that good. He is the areas go-to-bassist. He plays the bass he's told to play at session work and in the music pit at the local theatres.
I have 53 basses and suck at playing. I own 2 Fender P Basses and a Fender Bullet Bass. I like 'em, but I obviously like other basses too that are quite different sounding. I don't make my living from music as I'm an engineer in the Civil discipline. My basses are not tools for me...they're more dope for my addiction or escape. Like it or not the P-Bass is the go-to-standard of the recording industry.
When you do session work you do what you're told because you're a contractor or freelancer for higher, not even an employee.
When you have notoriety and your own well known band or well known solo act you can call the shots because you're doing the hiring.
This question or statement from the OP is really geared to musicians who actually make 6 figures or more from music. Not weekend warriors and bedroom bassists.