Depends on what you mean by
a thing because I'd say it's still fairly niche but SS/FG seems that way to me anyway I guess?
I ride 95% dirt on All City Big Block set up with a bunch of Phil's and fattest 700x32s that'll fit; had I known about Squidbikes at the time I'd probably have gone Squid for bigger tire clearance but for the trails immediately accessible to me the BB is perfect - worked out so much better than I expected and with foam tire inserts my local trails have not presented BB anything I really wish I was on a squid for.
That said, I am kind of a beast (6'2 175, have run 1,000+ miles barefoot, climbed 12+ hrs/wk for 8 years, do mile swims off San Francisco without wetsuit...) and have been riding FG a long time so 700x32 over sloppy trails with no brakes is fun; for my wife, she did not enjoy even the chiller parts of my favorite local trails on city-oriented SS w/ skinnier tires so I'll be getting her a squid (SS with brakes, not idiotic brakeless FG like myself...).
May have shared here elsewhere but here's the bad idea in her natural habitat (before pinch flat ate that rear Panaracer):
