The infinite pool is a very niche market. Obviously, it is for people who
really like to swim for exercise; there are such people but they are few and far between. Serious swimming as exercise is something many people talk about but few people do. I live in FL and every other house around here has a pool (or is having one installed) and none of them are infinite pools.
Assuming you have the room, for the cost of installing an IP you might as well build an average sized pool, or as someone said above, a Jacuzzi.
The appeal of an IP depends on where you are in your life. The ads most often feature older people because
a) they are the ones who can afford to have one installed and
b) they are the population who tend to swim for exercise. As you get older, swimming is one of the least physically damaging exercises you can do and still get benefits from, as opposed to something like running which is beneficial but very hard on old joints.
As you might imagine, professional swimmers, olympic athletes, etc. use them all the time.
What makes more sense to me is the “Fastlane” product which effectively converts your existing pool into an infinite pool by giving it a current that you have to swim against. Again, this is not something most young people can afford.
