(Background - BS in Computer Science). Most non-degree mill CS degrees are about theory. My university had 1 "Software Engineering" program where you had to work as a team (not a required course). Obviously, working as a team in SW Development is very important in practically all projects in the corporate world. Given those 2 statements, no surprise that I learned more what I needed to be successful at my job in my first year of full-time employment that at school (not including the lack of "how to deal with all the business stuff that has nothing to do with real work" course). So, a 4-year degree is no indication of practical success (and in my personal experience) neither is a master's or PHD).
Yet, given all that, my guess would be that if you went to a vocational school, HR may well assume it's because you couldn't get into a "real" college? And given what happened turn of the century - "I have a degree in HTML programming"-types - people probably are wary of applicants without any "proof" of real work. Given that the tools of the trade are so readily available (a computer), there's plenty of people out there who think they can program because of going through a few "program in VB in 30 days". A good technical interview should weed those out, but cheaper to first filter out people who don't even have a degree.
Now, there's plenty of cases where someone has the technical knowledge and no degree and has proved it, but sometimes job requirements are not bendable by the person doing the interviewing.