They actually would get more bang for their buck if they did take one car together, or biked (the majority of trips in the US are under 7 miles, and there are multiple options for carrying kids and groceries and gear on a bike), walked, and/or took public transit for some trips, and only used the vehicles when actually necessary. They would get even more bang for their buck if they didn't own multiple vehicles at all and biked, walked, and/or took public transit for most trips, and rented a/another vehicle when actually necessary. And kids can bike/walk/take public transit on their own long before they can drive, so this would mean considerably less trips to go pick up a kid and drive them somewhere else.
You obviously don't live in the US and don't have an idea how life is here.
Avg 7 miles? Are you insane?
Unless you live in one of the few BIG urban cities like a NYC or Chicago....that is just not the case..there is NO viable public transport....
And if there were, for example the other weekend I wanted to fire up my smoker....I bought a new 40 lb bag or so of lump charcoal to start my log burning offset smoker. I got myself a full untrimmed 12-14lb brisket, a chicken and a couple racks of ribs....some beer, and my weekly buy of normal groceries from Costco and couple other regular grocery stores, that had things I wanted on sale....how the hell would I get that home on a bicycle or public transportation that isn't door to door..?
By the way this type of shopping is not rare for me to do...
Renting a vehicle? When's the last time you did that....that is $$$ and you can't always depend on them having the type vehicle YOU want at the time....
Sure,, look...one CAN do things and bend over backwards to do theEV thing...but for the love of God, why would I want to put myself though inconveniences for my life...and pay more money for that privilege?