So I haven't read every post on this thread but I really appreciate someone bringing this up.
I am sick to death of hearing this crap from some of the guitar players I play with. "Why do you need two basses?"!!! bla bla bla.
When I lived in LA, every time I went to see a world class player like John Pena, Jimmy Johnson, Jerry Watts, John Patitucci, ....Brian Bromberg...shall I keep going?? They ALWAYS had a second bass on hand AND it wasn't always a fretless.
If these guys bring a second bass then NO ONE can open their mouth and doubt why I bring one.
I do a wide variety of gigs where up to hundreds of people are watching. When the audience is closely watching or the dance floor is packed and everyone is shakin' their booty to the groove, the last thing I want to do is kill the vibe by having to stop for 3 or more minutes and change a string.
The client is not paying the band thousands of dollars to have musicians show up who can't cover their chair. Sure if it happens I can make do on the other strings but at some point I'll have to change the string or it will most likely affect my performance.
I'm not doing bar gigs where an instrument failure won't ruin the event. I'm doing a variety of concerts and other social affairs where people are paying serious money to have the band as the main focus for entertainment.
Sure, I haven't broken a string in 20 plus years but a battery could go out!! The ONLY time I don't take two basses is when I'm flying or on extremely packed road gigs in the band bus where there's a serious physical threat to the instrument, in which case I pack one bass in a hard shell.
There....

now I've said my peace.