Parking lots are built and run out of a desire to get people to park there (so that they don’t go somewhere else). A garage owner is not going to willfully limit his customer base without a good reason. And “providing a happy parking experience” is not good enough. Driving and looking for parking is already not a happy feeling. It’s a case of “the customer is always right (even if they’re a dick)”.

You’d need the government to force these limits and then it’s not about just parking: it’s regulating vehicle size entirely.