There is a big crediblity difference between taking random classes and completing a program in a university.
The university has the onus to hire credible teachers, and to maintain a high reputation. You're paying for the standards they apply. Some universities aren't worth their weight and some are. The information that they have is out there. This has not changed. Textbooks have been arround for a while. Additionally professional teachers have the ability to communicate the material affectively.
Online classes can't guarantee a level of understanding of the material. Additionally online classes will never be able to guarantee that the person who signed up for the class is the actual one that gets the credit.