Solar panels are more popular the closer you are to the equator, so states like Hawaii and Arizona already have a lot of investment in solar. For the colder states, its financially a bad investment due to lack of enough sun throught longer periods of the year.

In population hotspots for example, in Socal, Solar is skyrocketing, but I wouldnt say they same for places like NYC.

I dont speak for other countries though, and wonder why some countries that should have it, havent invested enough in it (e.g latin countries, india) which receive a lot of sunlight.