That's the funny thing about anecdotes. You get to cherry-pick examples and make broad allegations from those cherry-picked examples. I'm a self-taught developer, and I've worked with plenty of "credentialed" developers that were either lazy as hell, having only gotten into software for the money, or were flat-out incompetent, again having only gotten into the industry for the money. That doesn't mean most folks with degrees are shit developers, it just means those ones were.
I think the real difference between the good developers and the bad is more a result of "passion" for the field. If your only care is about getting the job and the salary that comes with it, you may very well spend a lot of time and effort getting to that point, but you probably won't go beyond that. On the other hand, the guys on my team, myself included, are all passionate. Now that doesn't mean "slaves away for ungodly hours" or even that they spend their time working on side-projects. The common-denominator is that we very much enjoy the line of work. We try to be "craftsmen" and not just a desk-bound office rats. Some jobs allow you to get to a point where you just don't have to put forth much effort unless you actively try to be the best. Software development/engineering/ is not one of those fields.