Yes, perhaps that's true. It may have "always been done this way," and while not ideal, that's the way it is.
Much of this is fallout from the Griggs vs. Duke Power decision. Companies used to be able to sit someone down and give them an aptitude test for the job for which they were applying. If one did well on the test it was evidence that they were qualified for the job. The court decision said that aptitude tests that had a 'disparate impact' on different groups were unconstitutional. So the hiring folks had to try something else to determine who was qualified to do a job. The college diploma was chosen as a substitute indicator of suitability.