It is an action that can be done by an individual that doesn't require coordination with tens of millions of other people.
This is a real value that should not be underestimated.
With respect to you other points, yes, economies of scale and more ideal sites provide vast advantages commercial solar. Commercial solar farms are ~$1/watt and residential is $2-3/watt with subsidies.
Keep attention to an aspect: most setups are grid-connected because full autonomy is not possible or simply way too expensive. As a result while a single human can decide (depending on local laws on that topic) putting some panels and relevant inverters the grid need to cope with far less stable and predictable loads grid.
Keeping a grid up and running is a delicate balance between varying consumption and production, like having a tight rope with various needles suspended by the their eye, some with added weight, some with a hand to push the rope 50/60Hz. We normally "average the load" of a grid making large enough but not too large grids with few big generators and many small (or few large but constant) loads. With renewables and a gazillion of grid-tied inverters who tend to be (far) quicker than big ones the frequency keep a bit schizophrenic: inverters see constantly a bit too high or too low frequency and keep adjusting their output generated instability. If they are few others local consumers around them just absorb their output, but if they are MANY keeping the grid up is a nightmare.
It is an action that can be done by an individual that doesn't require coordination with tens of millions of other people.
This is a real value that should not be underestimated.
With respect to you other points, yes, economies of scale and more ideal sites provide vast advantages commercial solar. Commercial solar farms are ~$1/watt and residential is $2-3/watt with subsidies.