I rarely play my 6th string on my 6-string except for songs that have Eb or D notes. And to be honest, anything lower than D sounds like garbage to me. So there's not a big justification for it in my opinion. That being said, I like having it for when I play with guitarists who play alternate tunings of songs (usually 1/2-step down tuning), and I don't need to adjust my bass tuning. I can just play the half note lower on the B string.
I also don't like playing open strings, so the 5th fret E sounds better than an open E to me.
On Fenders early 60s Bass V five string bass, the B string was tuned to C, any of you 5 stringers tried that,its only a half step. The guitars fifth string is tuned to B so the sixth string is two Octaves above the low E and maintaining tuning in Fifths
I guess either you haven't heard or noticed when they do, or they just wanted that particular bass and it happened to be a 5 string one. The bassist from Alter Bridge uses his B string
