I fish a lot in the park and I've been checked probably 4 or 5 times out of maybe 75-100 days over the last 2-3 years. Not a particularly great percentage but the park rangers have a lot to do other than checking licenses. Whenever I do get checked, I make it a point to let them know how much I appreciate them being out there enforcing the regulations.
It really is sad how much illegal fishing goes on. I wish that handing out regulations would be a good solution, but in reality the people that are doing this mostly wouldn't even bother reading them in the first place. I don't think it really crosses their minds or else they are of the "I should be able to catch them however I want" mentality.