Many people do have sex with people they're not attracted to, and many people do not have sex with people they are attracted to. The distinction is useful.
Consider: https://en.wikipedia.org/wiki/Men_who_have_sex_with_men
Consider: https://en.wikipedia.org/wiki/Men_who_have_sex_with_men
I'm personally in the camp that if you have sex with genders outside the opposite of your own, then you're either gay or bisexual. I don't differentiate between whether you're attracted to the same sex or just seriously, uncontrollably horny and desperate to shag anything with an orifice.
I guess I still don't see the relevance of a distinction beyond that of psycho-semantics.