The pharmacy degree is very difficult to get from what I understand (years of effort and limited opportunity) plus each pharmacy is required to have one on staff. So one aspect is a supply/demand. Secondly they take on some legal responsibilities so if things get screwed up they are at fault. They are there as a safety check and to resolve any ambiguities in the prescription. Much of this is being automated by computers now. Lastly they give out advice. You don't want to read a 5 page list of rare side effects...