I think it’s pretty clear that seminary in EY is really nothing more than a trend that has been fueled by affluence and solidified by peer pressure. On its heels, an entire industry of seminary-related businesses have sprung up and an increasing portion of the frum ecomnomy is being tied this trend. As with so many other economic trends, it is the middle-class that gets crushed to the point where the frum middle-class now has yet another unaffordable “must have” with which it must contend, along with all of the negative things that come along with it (job stress, sholom bayis stress, stress-related health issues, etc.)
…and Shindy, I don’t thnk there has been an increase in the number of girls staying home. I think if you take a casual survey of people you know, you will find that over the last 10 years or so the percentage of girls in a typical northeastern Bais Yaakov type graduating class that go to sem in EY has increased from about 60% to over 90%. The trend is so near-universal at this point, that american seminaries are actually closing down because they simlpy can no longer attract a critical mass of girls with which to run their businesses.