There are down payment assistance programs that can provide a 3.5% down payment for the borrower, if they qualify which equates to a "zero down" mortgage.
Brian, down payment assistance is a great option for many homebuyers! We have some info about DPA here: https://www.readynest.com/getting-ready-to-buy-a-house/down-payment-assistance. A "zero down" mortgage could be an option for some, but not all borrowers will have access to or qualify for that kind of DPA. Building up savings means more options for homebuyers, or for anyone who might have a big purchase in their future!