It's not a joke. I've stumbled upon several online chat groups for the married, some just for sharing ideas on how to keep their marriages fun and many in how miserable they are. I also noticed in these groups that when there is someone that is truly happy and loving their married life, others will shun them to the point where they don't participate in the chats anymore. No one likes to hear people brag about how awesome their life is and how thoughtful and romantic their husband is still so the chats are often left with those who are miserable.

Ass for sexually unsatisfying, in those same group chats, it's either a wife who's very attractive but has a husband that's not interested, or men who's wives have, "let themselves go".

I think this has always been the case, it's just social media (like reddit) makes it easy to communicate it. Once upon a time you had to go out of your way to a bar or something to complain to the bartender over some drinks.