I think all the Vermont state parks (with showers, which are practically all the ones with campgrounds) use quarters for the showers--at least, that was true as of a couple years ago.
My understanding is that you get plenty of time, water flow, and hot enough water for your quarter or two; it doesn't seem to be a money-maker for the park, but probably more a way of preventing people from hogging the facilities excessively.
Being a cheapskate, I tend to use the shower in my RV instead when the park showers are pay-to-use.