I didn't mean to suggest that this always happens to me. I've had plenty of FAs on my flights who were perfectly professional and appropriate. I have, however, noticed the phenomenon described with some regularity.
I also think it speaks to a certain accepted, habitual immaturity in our community. The banter I've described is often flirtatious in nature. I can't imagine that a straight male FA would feel comfortable flirting with a woman sitting with her husband (but I certainly could be wrong).
I also am confused by the focus on gay nightlife in these encounters. My partner and I travel to see museums, eat regional food, experience other cultures, and of course to rack up miles.