At first, I was thinking you were talking about style checks, but obviously I am wrong. I think you'd be surprised how many people do that. The commuters in SF often do double takes (including myself) when they see a purty fixie. Matter of fact, yesterday, while parking my bike, a guy in a motobecane fixed rode up to park and we talked about each other's bikes for a bit.

Anyway, yes, I do look at other bikes also and sometimes even think, Oh, I 'd like that.