As the statista.com report says >...Rooftop solar photovoltaic installations on residential buildings and nuclear power have the highest unsubsidized levelized costs of energy generation in the United States. If not for federal and state subsidies, rooftop solar PV would come with a price tag between 117 and 282 U.S. dollars per megawatt hour.
https://www.statista.com/statistics/493797/estimated-leveliz...
Looks like that report is a year old, but I doubt the installation costs have really gone down much since then. (Panel prices come down, but labor costs, etc don't.)
Providing the infrastructure and reliability of the grid is very expensive, so there is a huge difference between the wholesale costs and retail rates for delivered electricity. Money is limited and is fungible - a dollar spent subsidizing utility solar will go much, much further than a dollar spent subsidizing rooftop residential solar.