I doubt there's a niche in all of cycling that attracts more widespread casual interest than fat bikes. I can't ride my Moonlander (see below for the Thill family fat bike fleet) anywhere without people staring, commenting, or asking questions about it. I assume that most of the looks and commentary, which usually seem pretty innocent, are not generally from avid cycling enthusiasts, but non-cyclists and casual cyclists. This doesn't happen to me when I'm riding my other bikes.
The questions and comments start to get a little redundant after awhile. What's that bike for? How much do those tires cost? Isn't that hard to pedal? Isn't that made for snow? Wouldn't skinnier tires be faster?
Well, I sell these things, and I ride my Moonlander year-round, so I feel pretty qualified to address the speed and "hard to pedal" questions. Every person who takes a first ride on a modern fat bike almost universally expresses surprise that "it rolls a lot easier than I expected". Most of my riding is commuting, and I haven't noticed much difference in how much time I spend riding the 7-ish miles to and from work on the Moonie compared to riding the same route on my other bikes. In fact, some of my quickest commutes have been on the Moonlander, usually when I was in a hurry, running late, etc. I will admit that the fat tires feel pretty slow going up big hills, but that's just basic physics - weight really only matters on hills, and fat tires and wide rims are relatively heavy compared to skinnier tires and rims. I suspect that I would be faster on a lighter bike with skinnier tires if, and this is a big if, I was trying to be fast. If I exerted my full effort, a lighter, skinny-bike would probably shave a few minutes off my commute time. But let's be honest, I haven't exerted my full effort in years, and shaving a few minutes off my commute has never been a priority for me. Predictably, there are people who are interested in maximizing speed and minimizing the weight of their fat-tire bikes. With a pile of money, a person can now buy carbon fiber frames, forks, rims, and other featherweight parts, resulting in a fat bike that weighs 25 lbs or less. To each his own, but that's never been my cup of tea.
In my opinion, the great thing about fat bikes is that they aren't supposed to be fast, and for the most part, they haven't yet been tainted with that brand of competitive machismo. Many (but certainly not all) of the usual competitive types still regard fat bikes with a certain amount of uninformed scorn and take them as a joke unworthy of their attention, which is ok with me. These bikes are supposed to be, and are, great for traction, stability, control in unconsolidated snow/sand/gravel, etc. In other words, fat bikes inspire confidence. An experienced trail rider can confidently roll 4" 10psi tires over logs and other off-trail obstacles, while an inexperienced rider can confidently ride trails. What might have seemed impossible becomes not only possible, but easy and fun.
I read a silly article this morning that purported to explain fat bikes to the masses. The author trotted out the usual nonsense stereotypes about fat bikes being used to ride to the North Pole or across the Sahara. While those feats have been attempted and/or completed, in my scientific statistical survey, approximately 98.7% of fat bike riders will never be within 1000 miles of the North Pole or the Sahara. Most of us just ride them on trails, or on roads, or on beaches, or across fields, in the winter, and also during the rest of the year. Fat bikes are super fun and appropriate for a wide variety of cycling skill levels.