Gary has basically got in ahead of me there and said exactly what I was going to say. As a holder of a JAA ATPL I have a personal responsibility to maintain my own recurrent knowledge of all those things I studied for my ATPL exams - which certainly included a lot of information about ATC procedures.
Many other pilots I meet, however, have some large gaps in their understanding of how things work, covering a large spectrum from fuel planning requirements, to ATC related issues - such as the different services provided in the differing classes of airspace.