Do you call ahead to your destination when you drive a car to a privately-owned public-use parking lot?
If I want the best price out of airport parking, darned right I do (or in reality I usually book online).
I really see no reason not to phone, it's just part of the system, live with it, don't whinge! And it maybe applies to 1 in 3 airfields so there are plenty of places you can just drop into if you forgot.
G