If, on the other hand, solar panels were wired to produce, say, 120 V DC output (i.e., the cells or panels wired more in series than parallel), then lots of things get easier and less expensive. All the wiring can be of much lighter gauge due to the lower current. The losses in the inverter would be lower because of lower resistive losses and more of 1:1 voltage ratio. Some components (capacitors, FETs and IGBTs) may be more expensive because of the higher voltage rating, but that is a relatively small incremental cost compared to the cost of copper.
It seems to me that a lot, if not the majority, of new residential solar installations are grid-tied with no battery attached. It seems that the system should be designed to make that easier and more efficient, rather than tie ourselves to historical off-the-grid designs. Plus, if Tesla and others are designing new style batteries for this market, they can design them for higher voltage.