Unfortunately those states do not have much solar irradiance compared to states like New Mexico, Arizona and the like. This makes solar less cost effective. A system installed in New Mexico would pay for itself in 7 years; the same system in Ohio would take 14 years. It’s also not about sunlight, but cost of electricity. State and local incentives play a large part too. The real answer IMO is cost effectiveness.
When those states stop burning coal solar will have grid parody. Meaning solar will cost less than electric rates. Coal is cheap to burn for co-generation.