In Time's recent cover story about the incipient backlash against helicopter parenting, you learn that most of these trend-stoppers are prototypical Gen X-ers, now in their mid-late 30s. Approved parenting styles go through cycles, oscillating between the extremes of "let them be" and "always hover over them." It has little to do with what academics or writers say because there are always plenty of them who argue for just about every spot along the continuum. It depends more on consumer demand -- a "let them be" group of parenting experts can publish all they want, but if parents tend to have a paranoid mindset, the advice will only fall on deaf ears and won't sell many books. Best-selling writers are just giving people what they're asking for.
Maybe the cause is that when the typical Gen X member, born in 1971, reached the normal family-forming age of 25 or so, the world had become a lot less frightening. They surely had memories of the pre-'90s decline of civilization, but they were still pretty young then. You aren't really in a position to freak out about how safe the world is until starting a family becomes a possibility. So they looked around, saw that things were doing OK, rode the wave of euphoria of the recent economic boom that began in the mid-'90s, and figured that there wasn't much of a point in stressing out about their kids being abducted by aliens.
In contrast, Baby Boomers and the disco-punk generation (born between '57 or '58 and '64) came of parenting age when the civilized world was still going to hell, relative to the post-WWII Long Boom. Obviously these are just tendencies because there's still plenty of variation within generations. My mother, born in 1955, gave birth to me in 1980 when the society was still incredibly violent by recent standards, yet she did not flip out if I set off on my bike without a helmet, nor did she beat herself up if I forgot my lunch one day.
We'll have to wait and see if this thing keeps going -- hopefully it does -- but this may be one of very few cases where the '57-'64 cohort deserves more blame for ruining the culture, and Generation X more praise for improving it.