Zoning laws that discourage mixed use developments. One of the only cities in the US that works well with the more European style model of mixed use developments with apartments and businesses all next to or on top of each other is NYC.

I can understand residents not wanting businesses right next door, but how many cities ban apartments on top of businesses? That seems pretty common IME, but maybe I've misunderstood what I was seeing.

Multitudinous numbers do, via zoning laws. Many expect apartments or houses to be separate from businesses.

Parking minimums.

I could support that, though maybe not in a place that's unavoidably car-dependant. As you probably know, parking eats up real estate and drives up prices.