Why don't men liek it as much?
Because any woman, eregardless of size, weight, whatever, is beautiful. the female body, whatever its shape, is worthy of being photographed.
The male, on the other hand, unless you are toned and trim, just looks bleh. With my skinny, hairy legs, pot belly and scraglle of chest hair, I won't make for high-art, thats for sure!
But there's another aspect as to why women like to be photographed nude: option 4. It turns them on. They get a kick out of it. Been there done that...