It's only in recent years that I bought my first five-string basses.
This was partially a matter of self-defense. There was an open-stage night that I quickly found myself anchoring, & the only space more overpopulated than singers is guitarists.
And most of the axe-slingers seem to gravitate toward doing EVERYTHING in E. It's my job as bassist to add not only tone but rhythm, to help keep the guitarists together. In order to hammer/slide up to an E, I'd have to move up an octave & then be competing directly with all those guitars.
Bringing a five freed me. I could stay comfortably mid-neck yet have room to PLAY a little, & still provide a defined bottom under everyone else.
But really, on a four I don't rely on the G, preferring to move up (or down when I can) rather than lay over, so I considered having a three-string bass built, skinny neck & all.
So why not put the bottom four strings of a five-set on a four & call it good? Less weight, less wasted real estate. I'd enjoy hearing from anyone who's done this.