Until the lot is filling completely with some regularity, the presence of any number of abandoned cars costs the owners exactly zero. It’s only when abandoned cars (whose parking tab presumably will never get paid) begin causing the lot to turn away would-be paying ordinary customers that it begins to bite them.
Another thought:
Suppose the law in that state is that vehicles can’t be declared abandoned until a year has passed. The lot’s management may well have known for 10 months now that that car was probably abandoned after it had been sitting 1 whole month. But they can’t do anything about it until next month: that’s the first date when they can file to seize it as abandoned and then sell it to recoup their fees. From the outside observer’s POV, a car where the lot’s management is waiting on the law looks exactly like a car that management is oblivious to.
Further, assuming lot management can seize then sell these abandoned cars in a simple & cheap legal process, that means an abandoned decent saleable car is just as good as a paying customer’s car. Better even since that space is guaranteed filled for an entire e.g. year with no chance of it being vacant a single night and no cost of multiple credit card transactions, wear and tear on the entrance and exit gates, etc. An absent or dead customer is the ideal trouble-free customer. Assuming the abandoned car can pay their bill when it comes due.
The airport terminal parking structure where I used park at work costs $25/day now. A year there would cost $9,125. If we assume a 5% auction house fee to sell the car and a law firm charging $500 to handle the routine paperwork to support the seizure, any car that can be sold for more than roughly $10.2K is a moneymaker for the lot just by leaving it sit there. They’d be motivated to haul off unsaleable clunkers sooner, but again only if their lot regularly fills up and the clunker means they’re turning away paying customers.
Here’s a thread from a couple months ago on the general question of taking legal ownership of abandoned cars. It has some useful info from folks with actual practical experience.