I agree that there are several causes.

The sexual revolution in the 1960's screwed up the courtship process and our culture is still suffering from it. Before the 1960's, there were conventions for dating. The man always asked the woman out (or asked for her parents' permission, if she was young). You were not supposed to have sex before marriage. The man proposed marriage, the woman decided whether to accept.

In the 60's, the pill became available and all hell started to break loose. At first, it was just hippie stoners breaking convention, but premarital sex increased, and TV shows and commercials started popping up that urged women to ask the men out, take the lead in the relationship, and propose. The courtship process was disintegrating.

In the 1950's, college dorms were segregated by gender, and there were strict rules in place to keep the kids from being alone in the dorms. (There were still entire schools that were only for one gender, and chaperoned social events would take place so students from the men's college and women's college could meet.) By the 1980's, all that fell apart and college life made hooking up easy. Everyone was sleeping around in their 20's instead of getting married. This was supposed to make everyone feel more happy and free, but everyone stayed single longer and it didn't really work out that way. Lots of people were miserable with no structure for dating.

In the 1990's, two Jewish ladies from New York wrote a book called "The Rules" that became a best-seller and a national phenomenon. It was a guide for women on how to get married, and it essentially told women to reestablish the dating conventions of the 1950's. The book told women to stop asking men out, and it told them to delay having sex. It told them to stay in shape, grow their hair long, dress well, and be well-groomed. The gist was: be a girly-girl and play hard-to-get, because men have a natural instinct to "hunt" for a mate. Men don't want to commit when everything is too easy.

A lot of women followed "The Rules" and claimed that the book increased their self-esteem, led to better relationships, and indeed, led to marriages. But there was a huge media backlash against the book. Feminists said that the book was setting the women's movement back and creating double standards for women. Some of the "Rules" were well-intentioned in theory, but came across on paper as manipulative or rude. Oprah and Bill Maher trashed the book. SNL tried to make it look bad. The authors wrote 4 books total, based on feedback from their readers, but after one of the authors got divorced, the movement died.

More recently, there was an Abstinence movement in Christian communities. This is an agreement between the two sexes, and that's an improvement over "The Rules," which focused only on female behavior. Abstinence got tons of bad press and criticism too. Both movements helped a lot of couples, but failed to catch on in society at large, and that leaves us with lonely, disconnected people, turning to technology for intimacy.