I'd say that it's common enough, since low-depth-of-field portraits are fashionable. However, you have to distinguish between two situations: in a studio or other controlled situation where flash is the primary light, vs. outdoors where you are trying to overpower the sun.

As the questions you've linked suggest, the studio situation is easy, but if you need to balance or compete with very bright ambient light, physics dictate that there is only one answer: a brighter light. And because that is difficult, the easiest way to get the flash to be relatively brighter is to reduce shutter speed, and then that runs into all of the problems of high-speed sync.

Even if people really, really wanted to do this all the time, those things are still hard. So, it's sort of a chicken and egg problem. On the one side, there's incentive from people who find the look useful/interesting and probably do want to do it more, but that's balanced by counter-pressure from the inherent difficulty and expense. Basically, I don't think there's anything significant at work beyond those things, and it's likely that the marketplace is roughly at the equilibrium point between them. In fact, I'd go so far as to say that the options which are available (powerful flashes with HSS) are actually reflective of your assumption — the technique is popular enough to support what is on the market, and not significantly more or less.