I think it's because mothers, understandably, want to be able to control their little boys. When those lessons and strictures carry over into adulthood, however, the problems that result for society as a whole are huge. With so many fathers either absent or spineless these days, there is often no male presence there to say, "Leave the boy alone, Marge - if he's going to grow up he has to learn those lessons for himself."
Perhaps the widespread military service undertaken by 17-18-year-olds in past geneations made a difference, and helped a larger percentage of young men establish themselves as independent individuals, free of Mom's apron strings and her teachings on romance. In these days of the "slacker culture" where it isn't uncommon for 30-year-old men to live with their parents, something is broken.
Very true!
I learned one, and only one, lesson about women in the military.
There was this nice girl around the godforsaken post that everyone in the company was drooling over, but other than cheesy pickup lines, none had ever really interacted with her. I mostly ignored her because I was young and she was way out of my league. One day when we were out and about on liberty, I saw her upset about something standing by herself while I was looking for a place to buy beer or some such. Already topped off with minor amounts of liquid courage, I asked her what was wrong mostly as a courtesy and started talking to her. Being the only guy in the area that talked to her like a real person, she latched onto me almost immediately.
When I walked back to the rest of my guys with a case of beer under one arm and that girl under the other, well, the expression on their faces was priceless. I did not do anything with her other than make sure she had a good time that night -- I'm not that kind of guy, particularly with a girl I perceive as emotionally vulnerable like she was -- but it kind of shifted my perspective. I owned that girl at that night. It also made me a minor legend at my unit. The only difference between me and every other guy in my unit was that I actually talked to her without being a jackass, and that made all the difference. I was honest, confident (in that instance), and not a complete sleeze, and that was all that was really required other than some good timing.
That incident convinced me that any guy can "get" any girl given some basic skills and decent timing, and permanently altered my perspective. At that point it becomes a question of selecting an appropriate girl to have a relationship with, not what girl you can "get".