Generally if you live downtown, you don't drive to other downtown locations. But, yes, there could be need occasionally, but probably not both both cars in a family? I don't know. My wife and I OCCASIONALLY will meet with 2 cars, but it's maybe 1 in 10 times, 1 in 5 on a bad month. But we are near suburban. The people I know that live in DT areas have 2 cars, but one usually has so much dust on it, because it just sits in the underground parking spot below the building. My friend who lived in DT DSM only drove for 3 years to go to the airport. Friend who lives in uptown MSP takes bus to DT MSP, because it's chepaer thn dropping $8/ day for an outlying ramp or $20 for an in-building ramp.
I can see needing 2 or 3 for a person household, but not 4. But DT areas, I agree that parking is truly are for incoming people. But an 8% fill rate at a downtown garage is bad.
I think the point was that it would be better to drop the billions on SOME sort of public transport system over that. But the spread of cities makes it a bit difficult - we need to hit too many places in a day or week for public transport to work for all situations. the daily commute is one thing, entertainment/visitors like you mentioned are another. If 4 spots are availble for every 2 cars, that's a 50% fill rate at any given time. It's that 8% that got me - 8% fill rate is PROFITABLE. I need to open a damn parking lot!!!
if you and your wife have jobs that you drive to (assuming you aren't carpooling), then you are using 4 parking spaces per day minimum.
that 8% fill rate sounds a lot worse than it is. again, these kinds of parking structures are necessary for tourism and events. they are made for overflow, not regular use. your not going to park in a residential complex's parking garage to go to an Iowa-Iowa St game and people aren't going to park next to a tourist attraction to go to work when their work has a garage. since there are practically no running costs to running a garage, its far more efficient to build garages to hold the surges in parkers than to build a transportation system that many people will never ride because they are either too attached to using cars or think public transportation is for poor people.
i'm all for more public transport but i disagree that surplus parking stands in the way in any way.
but yes, if you can manage to afford a downtown lot pretty much anywhere in the US, demolish anything standing on it and just pave it, not even build a garage, you will make a tidy profit.
this article doesn't really account for the need for parking spaces both at home and at work. there's an average of 2 cars per household, there should be about 4 times the number of parking spaces to households. add on to that needs for tourism/event-related surges... you get a need for a half million extra spaces in a downtown.