Anytime you see a plot that is just a parking lot with an attendant in a dense city, that is just a land speculation play. That parcel is still extremely underused, but putting a parking lot on it lets the owner extract some rent in the mean time. A land value tax would ideally be high enough that the owner of that plot would be losing significant amounts of money even with that parking lot there, and would be incentivized to sell it to someone who wants to actually develop it immediately.