Tops versus Bottoms

Why do some guys who claim to be bottoms (oral or anal), show pictures in their online profiles of their dicks? As a top, I'd much rather see their ass or their mouth. I mean, in the sexual context, a top usually couldn't care less what his partner is 'packing'. Same question in reverse. Why do some guys who claim to be tops, show off pictures of their asses and not their dicks? I mean, how much sense does that make? Alternatively, why do some guys say they are "total bottoms" and then after you start seeing them, suddenly express and interest in topping? Again, same question in reverse. Why do some guys who claim to be total tops, throw their legs up in the air at the slightest provocation? I just don't get it.