To reduce cost ( improve volumetric efficiency of transformers) such voltage conversion are done at much higher frequency. Side effect is lots of switching losses. Diamond based semiconductor are coming but that will take time.
The size of a high-power 60 Hz transformer is prohibitive in weight, both directly (where are you going to put it?) and in impact on price (shipping, amount of metal).
It ends up lighter, cheaper, and not much less efficient to do a high-frequency conversion instead, either as a boost directly from the 120V AC or as a DC-DC in the secondary.
At least for li-ion, the infrastructure problem isn't too terrible, as most cars will have an endpoint with high-voltage, i.e. the workplace.