I see nothing wrong with it aside from the social norms that make it "weird" or "bad".

The same could be said about homosexuality. Although I've never personally sucked a dick, and have no plans to do so in the foreseeable future, I think believing that it's "gross" or "nasty" simply speaks aloud about insecurities, and homophoia. People get really worried if they pride themselves on being a he-man and have to worry about whether or not they'd like it if a guy sucked their dick.

Seems like if you were a swinger, and did it only with people you knew really well it'd be a pretty good way to avoid marital boredom, and resolve sexual tension between two people who'd otherwise cheat on their partners.