One of my family therapy
texts proclaimed this and I tend to agree with it for two reasons: the changing purpose of sex
and the intertwining of employment
On the first point: Previously, sex was about procreation, not recreation (however, I admit this point can be argued). Sex therefore didn't have the accessibility it now does. Two men can discuss their sexual adventures today because there isn't anything fundamentally life changing about it (whereas, having a kid would have that impact). It's just like talking about a round of golf over the weekend -- did you play well or not?
While some might feel this change in sexual attitudes cheapens sex, I wholeheartedly disagree. Sexuality has its social components and deserves to be talked about... but I'm digressing.
On the second point, employment is very closely associated with identity. When you first meet someone, inevitably the question is asked: "What do you do for a living?" In the past ten years particularly, work has become more dominant in many peoples' lives. Socialization is done at work, and friends often come from work acquaintances or connections. And most importantly, social worth is often drawn from a person's job. An engineer often holds a higher place in the eyes of society than a garbage collector. Generally, with jobs of high esteem, more liquid wealth is on hand and can be spent. But couples often hate to discuss this because much more than sex, wealth is firmly associated with the ego -- and discussions dealing with the ego tend to end badly.
And who wants to discuss sensitive ego-centered matters like money, when they can enjoy some recreational sex?