If you want one rooftop’s worth of electricity, you can either pay someone else for a rooftop’s worth of real estate and have them run solar panels on it, and transmit the power to you over wires, or you can put solar panels on the rooftop-sized area you already own at zero marginal land cost, and have the electricity already right where you want it.
That that works out economically doesn’t seem like a surprise.
Solar panels are rapidly falling in price, and now I'm generating the power right where I'm using it - so no transmissions losses, no power transmission infrastructure, no transformers, no poles to replace when they get old, no lines to replace when trees fall on them, no trees to trim. No accounts to maintain, no billing, no credit card fees, no taxes. In fact, to get power to my house for the next ~30+ years requires absolutely zero labor from anybody.
Of course it's economical, it would be baffling if it wasn't.