The apartment one isn't really different. The landlord thinks they have more to lose from tenants complaining about lack of parking than your girlfriend cancelling her lease because you got towed. Maybe towing within 15 minutes is too strict, maybe it isn't, but it's the landlord's business decision to make.

With the closed businesses, you have to remember that the effect on the business isn't zero. Lawsuit society means slip and falls, muggings when the lights are off for the night, etc. result in getting dragged into court and paying for a lawyer even if the plaintiff doesn't win. They may need the lot open for deliveries, cleaning, or night employees. How do they know an overnight parker will be gone by opening? The problem is once they allow parking, even if not explicitly, the genie is out of the bottle.

But even if those things aren't a problem, it's still their right as the property owner to say this is MINE and you can't be here without my permission. It's no different than someone parking in your driveway without your permission. Plus if the other local businesses really thought they were losing money, they could work out a deal to use those spots.