It's just a British thing, I think, not to want to know about people's private lives. It's the same reason why people who speculate on the wealth of others are seen as vulgar.
I've considered this but rejected it. At least for here. There isn't a poster here who hasn't divulged into speculation into someone's personal affairs in some guise. Yet it's routinely only homosexuality that gets the 'It shouldn't be mentioned' replies.