I'd have one if I was well versed in SW and wanted a seahorse tank, but for FW they're kind of a pain. I've seen some corner tanks that are sort of a hex shape for sale on CL, but no ones buying them either.
It's purely an opinion thing. People like them or they wouldn't be sold. Supply and demand.
"What, exactly, is the internet? Basically it is a global network exchanging digitized data in such a way that any computer, anywhere, that is equipped with a device called a 'modem', can make a noise like a duck choking on a kazoo." - Dave Barry