The problem is that the resume and candidate pipeline is so crappy, that the interviewer cannot be sure if the person sitting across the table is a doctor, or a plumber, or a carpenter, or an accountant, or maybe a bum off the street.
My interviewing life would be a lot easier if there was a firm guarantee that every candidate knows at least basic programming - and by basic I mean basic - i.e., can put together a for loop that compiles, in a language of their choice.
The second part of this problem is that the industry has so many jobs where the absolutely clueless can survive that "X years experience" in-industry is not a trustworthy metric for competence. "5 years at County General" for a MD, with a clean record, is a pretty decent guarantee that your candidate is in the ballpark. "5 years at Accenture" for a programmer guarantees nothing, not even the ability to write FizzBuzz.
Elsewhere in the thread someone mentioned being incensed that, even with his years of experience, he was being asked elementary questions. That's why - years of working experience is not a valid signal for competence.