This bears repeating. Driving in major cities is, to me, one of the most miserable experiences to be found on the face of the earth.
When city land becomes valuable enough that people in parking lots don't generate more wealth than they would if there wasn't a parking lot, the parking lots get sold and buildings are put there instead.
And yes most cities I've been to tend not to charge for parking at night or on the weekends.
I'm not one from whom to take advice on the subject, though. I think roads are for driving and parking on them is perverse and I refuse to live anywhere crowded enough to have a bus system.