Many AM sites are located in useless swampland, or areas where there is little to no growth. The AM sites that have shown value are located in areas where housing is being built, or industrial areas like the WMAL site.
Exactly, it's about urban sprawl, Beasley just lost two Florida stations -- took them dark -- to that end. At the time, Parkland had nothing out there but cows and horses. But the area grew and grew. Before you know it, their tower site was boxed in by apartment complexes. There was a plot of (one of the few open) land next to it. The city wanted both plots: station gone for a condo complex. Parkland, which was once considered "the country" in Northwest Broward is now a major metro area. It's shocking how far west into the Everglades they advanced.
Many stations -- all over -- are forced into dark or diplex (even find new studios) by way of office parks and condo developments.
Meanwhile, you move up state from Beasley's site, into Central Florida, then move west, off the populated coast, into the Space Coast and Treasure Coast areas, Amazon -- no one -- will ever vie for them. The small AMs there are south of nowhere -- with acres and acres and acres of open land with no signs of growth. Deep into Central Florida -- away from Orlando (Central Florida is a pretty large area) -- and there's miles of wide open spaces. Miles of it. Amazon -- or any behemoth -- would not want the land of a little station's land way out there.
Word is, MBRI of NYC is losing two to their station in South (West) Miami to the same problem. That geographical area boomed as of late. The land the towers sit on have been squeezed out with housing and apartments all around it -- and that community needs a shopping center/mall!
Then there are AM sites that are on a pretty tight plot of land in a move developed area, maybe boxed in, but you look at the area, the size of the land, and you can see there's not much you can put there, outside of say, a Wawa. The land is too slight to be desirable. You can't sell or buy up ALL the land. Some land just needs to left alone; stations need to put their towers, somewhere. You can't antenna farm or diplex everything.
Just find a station on Google Maps and satellite it. It's easy to guess which station will go to the way of urban sprawl and which will stand there -- with studio and transmitter in some cases, on the same spot -- for a long, long time.
As far as the fear of Amazon swallow up radio stations for the land to build warehouses: there's more than enough dead shopping centers on plots of land
larger than a station's tower site that they can level and build anew on. And they'd be near the people that can become their new workforce.