They are all high pressure, a feature that is now irrelevant for the majority of users.
Are they? I would have assumed that even before the boom in road cycling a decade ago that it was at least 50/50 roadies Vs MTB’s among the vaguely enthusiastic cyclists?
Then assume that people always like n+1 so MTB’ers would have a road bike as well.
I’d have thought most people would want/need a pump that can go to 100psi+.
And you don’t really want a gauge you can max out, it’d get damaged.
And you don’t really want a huge diameter barrel to shift more air, because the valve will always be the limiting factor.
The fact that only a few ~mtb specific track pumps exist probably says something about the size of the market. I used to have an SKS “29er” track pump, it was utterly useless.