Quoth Excession:

Energy storage isn't free either. Using batteries, pumped hydro, or something else still means a large investment to build that storage. You need that storage because home energy use is highest when it is dark.
Home electrical usage might be highest when it's dark, but overall usage is highest during the day. So when your solar panels are being shined upon but nobody's home to use the power, you sell it back to the utility company, which in turn sells it to the offices, factories, and other customers who are using power at that time.

Of course, the day-night cycle is predictable, and so it's easy to plan around that. More difficult is intermittent fluctuations due to clouds and such, and you still need some way of dealing with that. But even that might not need batteries or the equivalent: You can get a lot of flexibility out of smart metering and time-averaged loads. The idea is that some loads don't actually need a consistent power, as long as it's enough averaged out over some reasonable time interval, so the electric company continually varies the price of electricity based on production (i.e., cheap when the sun is shining and the wind is blowing), and those loads are connected to smart meters, so they know when it's cheap, and only turn on at those times. Air conditioning, for instance, is such a load, and is a major part of total usage in some areas (and it has the added advantage that the need is correlated with when the sun is shining).