All high-bandwidth wireless technologies are limited to line of site or near line of site. In the U.S. from the Southern Tier of NY down to Georgia and Alabama many people live in a landscape which is basically a plateau which is dissected by valleys.
There are no "commanding heights" in these areas, rather a tower on a ridge between two valleys may be able to see into those valleys and maybe the next two over.
Sometimes the top of the ridge is roadless so putting in wireless infrastructure is a matter of building a new road, a new power line, running fiber optic along the power line, etc. It boggles the mind to think that this can possibly cost less than running fiber along existing roads and power lines (either for FTTH or FTTN) but that's what the anti-fiber lobby wants people to believe.
If you're in some place where 5G is available it is probably a relatively high-density place that already has cable, in which case 5G internet service is usually trying to undercut cable on price. If you're in a place where WISP is a substantial option you're either in an unusually favorable urban location (the webpass model) which is vulnerable to millimeter-wave 5G or in a a rural location where the WISP is already a desperate measure and 5G won't be profitable.
A partial counter is that AT&T and T-Mobile have added a lot of low band spectrum in recent years that have some potential in Appalachian environments and served it with either 4G or 5G radios but the spectrum does not add up to a lot of bandwidth, particularly if radio conditions are unfavorable.