For one thing, it's a bit silly to set up a fancy new wifi alternative with much better signal isolation between APs and then run it over backhaul with none.

> Some places have interference but in situations where they work, they seem to be fairly well liked.

But that is the problem....

Power-line networking both suffers FROM interference, and causes interference TO licensed services. When it works, it works well, until randomly it stops working.

You can't expect to reuse allocated spectrum without encountering serious problems.