There's still (rural US) markets where 4G isn't reliable. WISPs can do great in those areas yet.
I never thought of WISPs existing elsewhere as it doesn't make nearly as much sense if you have access to "real" broadband. I suppose this niche was wider at one point?
Speaking as someone who used to live in Long Lake and had to drive to the edge of the hamlet down at a bridge just to get a single bar to check back in on family, I certainly wish the APA would loosen up a bit more on just letting towers go up.