With the exception of the one block stretch between Pine and Liberty, Nassau street doesn't have parking on both sides of the street. In fact when you get to Pine there's a security barrier and there no parking or cars allowed - all the way past the stock exchange.

For those who don't know how ridiculously narrow the streets are down there this a typical stretch of Nassau Street:

https://www.nybits.com/images/photo/nassau_street_01.jpg

So how do deliveries work to businesses on Nassau Street when you eliminate parking? They don't matter? What happens to the price of goods when their delivery becomes much more expensive? The block that does have parking on both sides of the street on Nassau is used extensively for deliveries. In fact if you do a Google Street view of it you will see a Fed Ex truck parked there. Arguably an important thing in an area that is largely financial companies and law offices.