In my case the superhot skew started when I grew Red Bhuts (at the time to me, the infamous "ghost chili") for the first year. My garden only had a few standard chile varieties at the time so this was truly exotic for me. I ended up really liking the flavor of the bhuts and despite having 4 plants I never had a ton of productivity from them so there was always just enough for personal use and for friends/family give aways.
Then it just slowly snowballed with a few more superhot varieties (multiples of each for redundancy) and in the case last year I had so many scorpions I was giving them away by the SFRB.
I don't think there was ever a conscious choice to "grow something I won't use" it was more a curiosity to find out what other superhots are like, and the uniqueness in growing them. Partial adventurer/explorer mentality and partially a collector mentality. The thought of usage was down the list.
So, now I'm thinking more about use and less about the capsaicin arms race. If a successor comes along to the Carolina Reaper then I probably won't actually try to grow it and leave that particular adventure for someone else in the hobby, with which I'll probably trade some of my unique, not-quite-so-hot, flavored peppers.