It will be mandatory on all flying objects eventually. The technology will become so cheap
Yes, indeed. But authorities keep on making it expensive and tiresome, not to say exhausting, to get any bit of avionics certified. As long as they keep to that policy, the equipment will be expensive, and offered only by a few.
which can lure some into a false sense of security
Which is my argument against them FLARM thingies, as nice as they look, and I won't deny they can contribute to safety. Under the eyes of a pilot (or team of aviators) who know its limitations.