My answer:
Video games and the related effect of kids never leaving their parents’ basements.
Also gayness - no need for both ‘men’ to work, in most cases, as they are usually well-educated (at least one of them), and their only major expense is make up.
That may explain part of it. I don’t know enough gays to know the trend- but I know of 2 male gay couples. In one couple one male has a very good job and his partner is an artist that does not seem to sell anything. The other couple one has a successful business and his partner is very much like the stereotype 1950s stay at home housewife.