The fact is, most people aren't builders and never will be. Building software is about formalizing and automating processes, and 95% of folks aren't interested in putting even the most basic effort into improving their business by approching it at a strategic level. Too focused on keeping the lights on and/or more interested in field operations.
For another example look at the many businesses using @gmail addresses to run their business while Google Workplace has streamlined custom domains for a while.
So in practice, ChatGPT Sites will mainly enable software agencies to build websites and offload maintenance to the customer : just manage it from your ChatGPT account. The equivalent of Bring your own cloud for Mom and Pop businesses, and other small companies. Not even sure ChatGPT Sites will create meaningful downward pressure on agency rates.
Lesson learned the hard way.