Essentially, when we strive to differentiate ourselves in a way that is abnormal to the majority of people, that distinction will almost always be used as a means of social identity. Whereas, being straight does not have a substantial impact upon the identity ascribed to them. You never hear people say, you know that straight girl from class? The lesbian in class, now that would be a different story. People begin to use these markers a means of describing and anticipating identities and behavior, whereas diminishing other identities which may be more substantive to our everyday lives. Thus, diminishing our cumulative identity, supplementing/changing that identity with something as arbitrary as who do you prefer to sleep with?
Further, straight people are less sexualized in that sense. When I think gay/homosexual/lgbt grad student vs grad student, I immediately tie sexual behavior to identity and perception, and its distracting. Or, I tie an expectation to studying "gay" subjects, which might be misleading or pigeon-holing.
Sexuality, the structured labeling, and the need for other to form social identities based on these is not important beyond personal/private dating preferences.
I actually don't even say "I like men", but rather say something like, "my boyfriend" "my ex...he". People know my sexuality, but I have presented it in a not important way, and people seem to treat me as more normal because of it. In the past, self-labeling set up those expectations and false attributes.
