pay for "hangover parking". Street parking Seattle only costs money during the day. But if you're out and about on a Friday night with out a designated driver, taking the bus home is safer for both you and the public at large. But then you're stuck with a parking ticket unless you can get back to your car before 8am the next morning.
Elsewhere, the city of Victoria, BC, uses parking cards both to eliminate the guesswork in deciding how much parking time to buy and save the city a few bucks on credit card fees. Several cities have shifted to smart cards for transit purchases, so adding the ability to use your smart card to pay for parking would be fantastic.