Installing a solar panel on a roof is not exactly expensive, complex, or difficult. Virtually every house in my neighborhood has them.
It might comparatively more efficient/cheaper per watt to build solar on the ground or on large commercial structures, but that doesn't change the economics for individual home owners, which in many parts of the world are already positive.
Money is fungible and not unlimited. A dollar given to you by your neighbors in their taxes to subsidize you would have gone much, much further if the money would have been spent to build solar by your power utility.
Also, it can be politically and technically expedient to provide incentives, even if it is not the theoretically most efficient use of that money. For example if it increases acceptance for renewables in the broader population or jump starts an industry (as it has in Germany).
When grid scale batteries drop in price, the substations can also store energy. Then the feeder lines only ever need to support the base load power draw.
Solar is so cheap, that even in off grid installations, the battery bank can be a fraction of what it previously would have been sized for. Modern batteries can be charged much faster and workloads can be shifted to the sunny part of the day.
