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, chicken and egg problem. People probably do want to do it more, and you'd think the free hand of the market would invent solutions, but it balances with the inherent difficulty and expense. 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.