I looked into this and the same photos could be compressed as nice color JPGs of the same size, with a lot more detail. But it would require more computing resources on the viewing end. I think this is their main target, hardware required to decode.

Not sure, JPEGs were fine in Netscape on my 60 MIPS 5x86-133 29 years ago. Mortification of the flesh to do penance for the sin of humanity tasting the forbidden fruit of knowledge may be their main target.