Well to answer the original question. Why other people buy them, could be all kinds of reasons, good ones and bad.
I can only speak for myself.
I bought a K2 Marksman a few years ago. It was my only ski. It is 105 underfoot.
I bought it because Blister specifically called it out as the most pivoty, slarvy ski out there. I also wanted something wide enough, to make skiing soft snow fun and easy, even with my mediocre technique.
It fits all those criteria. It is also fun to carve on hardpack, although it doesn’t have much bite on ice. Luckily I almost never ski that.
I would have considered a narrower ski, but I never heard of a narrower ski that had those same attributes.
Similar story again with the touring skis I just bought:
I bought Wayback 106.
I wanted >185cm (I am 6’5”)
I wanted a rockered tail.
I looked, and could not find a narrower touring ski with those specs, let alone one that had a solid number of real reviews to check out.
Finally, although a wider ski will suck when skiing steep, hard pitches, with a little luck you can wist for them to soften.
At the same time, I don’t always have good technique, so trying to ski a, let’s say, 90mm ski in waist deep powder or breakable crust, might not go so well for me.