A good reason would be that this blog caters to a lot of starting DJs. And RCF, by any standard set, does not qualify as beginner gear. The quality is beyond reproach, most rental companies will own at least a few sets. The price however matches the quality. As there is also a personal taste factor involved, I dare venture that for most RCFs you can find an alternative for a bit less money.
My personal favorites for years now are the Mackie HD Series. Currently I own two 12″ HD1221s and one 18″ HD1801 sub. Plenty of high quality sound and oomph for up to an easy 200 people.
Anything bigger I still rent.
Some other brands I love (especially in the larger segments) are German-made Fohhn (absolute wonderful column arrays with a ridiculously loud 21″ sub) and of course good old L’Acoustics.