Gepaine -
As you pointed out, almost every provincial park in BC has no hookups. It seems that you pay more for: washrooms with flush toilet and/or washrooms with showers. Other than that, I can't think of other reasons why there is such a discrepancy amongst parks.
Some parks are very popular and are situated beside or near recreational sites such as lakes, rivers, etc. and the charges here may be higher ????
It seems that State and Provincial park fees are increasing quite quickly and are not that much cheaper than many private campgrounds. I imagine operational costs are becoming burdensome for both governments.
We have a "goofy" reservation system and is not much more than a cash grab but that is another issue.
Actually, I don't think there is much logic in how fees are applied but it certainly isn't for "services" --- unless you call showers and flush toilets "services".