Each to their own, yes, indeed. Anyone choose whenever 5 strings or more is the overkill border that's crossed. Tony Levin chose 3 strings not to be overkill. However, when all things considered, it's a bit like the drummer- big kit or small kit - thing. If you're professional enough, and really skilled, and experienced, you can really show off your talent more, with just a small drum kit, with all the basics, one tom, on bassdrum, hihat and snare, and one cymbal. You don't need Terry Bozzios megakit to be able to pull it off.
The legendary bass players throughout the history, that has been influential for youngsters to start play bass, or influenced a whole generation of bass players, didn't start out with 5:ers or more strings. Very few 12 string "monster players" - if any - has "woved" others to go "Hey, I must learn to play....that extended instrument thing".
But as everybody else said, and what's the thread is about, is reminiscent of drummers - as experience grows - DOWNSIZES from a large drumkit, say with double bass drums, or one or two toms too many, and they go "I don't REALLY need it". When they themselves discover that that one extra string is superfluous, and ... overkill. Not really much more to it than that. There's sure a thing to it, the smaller the drumkit, the more you have to use your imagination and creativity to work within its limitation rather, than the other way around, that the more strings the better options you have, and you don't have to think about it that much because it's already there, all these colors, variations on scales. For example, if I would HAVE TO play these 3 strings basses used by Tony Levin, I would force myself to play artifical harmonics a bit more to reach these upper notes.
On a side note, I've always had a bit of resentment towards bass players, professional or amateurs alike, that stops playing- when playing live - just because of one of their strings snaps in the middle of a tune, and actually demands that the rest of the band stops playing. It happened the other week at a gig I was sharing bands with, the bass player even played a fiver. He had to take a break to change out his g-string! I am not that kind of bragging people but this was the first time that I thought "You wont EVER find me doing that, ever!!" Christ, the bass didn't go out of tune either. There was no other mitigating circumstances either, since the combo did just play blues standards (3 chord blues tunes). It was a seasoned bassist too. Like 40 plus something. That's a big no no in my book. On guitar, if it goes out of tune when snapping a string, it's more understandable, but anyway.
So by and large, I think people who have played 5ers and 6ers (or more) for a while, and then resorts back to 4 or less, have discovered, it has dawned on them, that their skills and experience has improved and doesn't really need more. It's always been in that direction. Never ever heard, that you need MORE (larger drumkit, more strings) in order to prove that your musical skills and virtuosity are improving. It's always the other way around. The LESS options available at your disposal, the more professional you are. I remember one interview with Pat Metheny Group drummer Antonio Sanchez when he was at the unviresity. He played in a big band setting, but tried to bring his huge Neal Peart drumkit along. And started to play and went all over the place. Showing off, and as fast as he saw a cymbal, he would hit it. And his drum teacher, got on stage with a wrench, and started to remove tom after tom WHILE he was playing. After a while, he was down to the most minimal drumkit, and it all started to sound much better. Antonio was outraged at first, but after it all, started to get where it was aimed at. Lesson learned.