You're replying to a comment about the true cost of solar being the battery + the panels, asking why anyone would think of buying a battery.
That's why.
That's why.
If I move to a house with solar panels, I budget on power costs = cost of grid connection + X * grid power price + (1-X) * solar price (which is the capital cost of the panels smoothed out over their useful life).
The issue here is that I can't maneuver into a situation where my power price = solar price without sacrificing my ability to do anything after sundown without candles. Clearly, the true cost of power in a solar-enabled house is going to be higher than the cost of the solar panels.