Electric drier plugs aren’t always conveniently located (and some won’t have any—apartments and certain types of assisted-living sorts of situations might not).

Normal outlets take forever to charge. Days from, say, 20% charge to get to full. Better not be using it for any other driving while you visit.

May have to kick one of their cars out of a garage, in either case, to reach any outlet. Some people really hate having their car outside.

Dunno how long your trips are, but if you're staying 2-3 days an L1 charger should do the job even if you drive around town a bit while you're there. I also keep an extension cord in my car, which works well for running under garage doors.

Generally, we're driving out, hanging out for a couple hours to have a meal, and driving back. There's no garage to plug the car in; the car area is about 100 feet from the house. Overall, it's just not realistic to plug a car in while visiting them.

If you came to visit me, you couldn't charge your car where I live. I don't have private parking, and the places you can park near me do not have any access to a plug socket. Not everyone is lucky enough to have appropriate infrastructure around them.