If I were applying for a programming position, and the interviewers did not try to verify that I knew how to program, I would be very concerned about the group I was interviewing for. I prefer to work with competent people. I would like to believe that my prospective employers used due diligence in hiring.

As a programmer myself, I can get a much more credible idea of someone's skills by watching them for ten minutes while they try to write fizzbuzz or linked list reversal, than I can get by reading any number of letters of reference, or looking at their college GPAs.

Not every college and university emphasizes practical knowledge. It is entirely possible, at some colleges and universities, to get high marks in theory without acquiring much in the way of practical skills. It is equally possible to get good references from employers who would be glad to see someone gone.

I'm the director of a small CS/IT Master's program which does emphasize practical skills. As such, I'm delighted when prospective employers test my students; it gives them a nice advantage in the marketplace. We have an enviable placement record.

Bottom line: Why take someone else's word on an applicant's capability, when it's easy enough to observe it directly?