Why? Several reasons, IMO...
1. Some people don't like how they feel. Running your fingers up and down a piece of plastic (well, nylon, really; but, you get the idea) does feel kind of... weird. Especially if you're used to running them up and down a wood rasp... er, I mean, roundwound strings...

2. Some people don't like how they sound. I
think they were developed by Rotosound, and the reason they call them "TruBass" strings, is because they were intended to sound like an upright bass. While they will never sound
exactly like an upright, on the right hollow body bass, and with the right playing technique? They can sound... reasonably close. My MIK Rogue VB-100 violin bass wears the Roto tapes, and when I want it to, it's close enough to make me happy. However... most electric bass players want all the sustain they can get, and
don't want to sound like an upright bass...
3. If you want to use tape wounds, you will almost certainly have to widen at least the E string nut slot. You might have to widen all of them; I did, when I put them on my Carvin LB-20 about a decade ago. And, when I put normal flat wounds on it, I had to replace that nut. Some people simply don't want the aggravation...
And..
4. I've never had the problem myself, but... with tape wounds? Grounding issues seem to be a problem for quite a few people. And, understandably, very few people
want grounding problems with an electrical thing in their hands...
So... if you want strings that are all about "Thump"; don't have much sustain; require you to hack up your bass's nut; and make weird buzzing noises until you touch them - because, now
you are the electrical ground? Well, then, tapewound strings are the strings for you. Several string companies make them... choose your poison...
Seriously though; I've had the Roto TruBass88 Tapes on my violin bass for... about 14 years now; I've never had the slightest problem - of
any kind - with them. They sound great on that bass; I never play rounds on anything, so I love the Roto's feel; and, if they're good enough for Sir Paul on his Hofner (and his Rick), they're certainly good enough for me. I took the La Bella Black Tapes off my Carvin, not because they gave me problems or sounded bad; I did it because it was strung BEAD; I and, I realized I just didn't need a bass strung BEAD. So, I took them off; put the original nut back on (I'm... prudent, that way); and put a set of flats on it instead. I play it a lot more often, now... But, if I wanted a deep, woody tone - with minimal sustain - from a bass - and I didn't want to put flats on it? I wouldn't hesitate to put a set of tapes on the thing...