>if you keep allowing more people into the neighborhood with cars it becomes impossible to ever find a spot.

That's absolutely true, but the solution isn't to force new construction to provide parking; that gives an unfair subsidy to people who have lived in the neighborhood longer (and choose to own one or more cars). They've been able to store their stuff in the street for essentially free for decades, and everyone who lives in the neighborhood has an equal moral right to the free property storage (even if they just moved in yesterday).

Let builders build what they believe they can profit from, and manage the parking separately. Either increase the cost of a parking permit until you get the number of cars that street parking can sustain (the capitalist solution) or implement a lottery and tell people who lose that they just aren't allowed to park their car on the public street (my preferred solution, but politically untenable).

In terms of "fairness to the people who already live there", the sooner we lost this idea that their house came with guaranteed free and convenient parking the better.