People also like AM crystal radios too, because they are simple and cheap.
A super-regen is an AM radio. AM makes static sounds and has other interference. A super-regen sort-of detects FM if it is tuned to one side of an FM station but then is noisy with interference and high distortion.
Like an AM crystal radio, a super-regen has only a single tuned LC network that picked up the only station in town long ago. Now-a-days it just picks up all the stations at the same time.
Long ago, a super-regen could be adjusted so that it isn't overloaded by the only station in town being too close. What are you going to do with its overloading by all the stations today?
If you are anywhere near a large city then you won't like a super-regen.