I think I'm starting to understand the reasons for that.
It's not professionalism, or talent, or grit.
It's that being a neopro sucks in a lot of ways. It's hard work: you're out there scrabbling, bringing home the occasional paycheck, trying to convince yourself that what you're doing is worth the time you're not spending with your s/o and your dogs... and it's hard. It's hard because the rewards are so few and far between, and there's no guarantee of success, and you know perfectly well that you just may not be good enough or in the right place or writing the sort of stories that the available editors want to buy. And so much of it depends on stuff that isn't even "write better."
And the temptation is there to quit. And a lot of people quit. And a lot of people who don't quit struggle on for years and experience at best modest success.
That's why I think online writer's resources are so valuable: that peer pressure helps keep people producing, submitting, growing, talking, increasing in skill. I think--I see the evidence in my slushpile--I think we're raising a formidible generation of genre and slipstream writers out here in etherland, and the ones who don't crack are going to be a force to be reckoned with in five, ten, fifteen years.
It's going to take five, ten, fifteen years.