Sure, the first order effect of minimum parking requirements is that there is more parking, which is nice in a situation like the one you describe. I don’t dispute that.

What are the second and third order effects and how do those effects compare with doing nothing? Will these laws be revisited as modes of transportation and the urban environment changes? (Spoiler alert, no). Without these laws would everyone just be permanently unable to park? Or would tenants, knowing how hard it is to park in public spots, pay a premium for private parking? Wouldn't those premiums incentivize developers to add private parking? But unlike the legal remedy, when those incentives go away, we don’t have to keep building parking spots.

More tenants would forgo owning a car and walk, bike, use public transportation, or call an Uber.

   "developer builds 50 units without parking expecting the neighborhood to absorb the cars"

That's exactly what's happening in downtown San Jose right now. One specific example::the city is approving a big new hotel on a tiny lot next to the De Anza Hotel with absolutely no parking provided, externalizing that mess onto the already parking-deprived neighborhood. SAP Center event nights will get really interesting.

Which should also lead to a broader consideration of “why do so many people need cars in the first place?”

Well, yes, but until we fix something at a societal level which takes decades some poor people on a given street struggle because all the new buildings increase people and car density but not parking space. Which means, it makes sense to apply the rule first, and then fix society and then we can turn that excess parking space in gardens if need be.