Earlier quoted context omitted.
it's because they are mothers with >2 children. You cannot fit three car seats in the backseat of modern sedans, and station wagons don't meet the emissions requirements. Large SUVs meet CAFE regulations by being large enough to be regulated as a different class of vehicle. Want smaller trucks? Complain to your Congresscritter to reign in the EPA and force them to write better regulation that does not have these unin…
There are WAY more trucks/SUVs out there than 3-child households. And I'm not sure what you mean by "wagons don't meet emissions requirements" - wagons would meet the same regulations as sedans.
Note that I used the Mercedes because it's the only non-compact wagon I'm aware of for sale in the US.