Canadian RV Parks just don't seem to get the snowbird lifestyle. As a Canadian we can NOT spend more than six months in the U.S. I don't want to get into the formula for the exact length of time here. That is for another thread.
My point is when we book a seasonal sight in Florida for six months from November 1st it is to April 30th of the following year. When we book a seasonal site in Canada the parks don't let you in until May 15th or 24th and close on October 15th or the Canadian Thanksgiving. We pay, on average the same as we pay for a seasonal site in Florida, Texas or Arizona.
We understand some of the particularly issues of northern climes such as water lines potentially freezing in October and are willing to work around this by bringing in our own water or whatever is needed.
I think it is a matter of greed. They know they've got Canadian snowbirds right where they want them so they can squeeze them. However, most parks just will not open earlier or close later so money isn't the issue with them.