But is it still expensive compared to the situation where you're buying fuel for the ICE instead? For many places, the saving on the fuel costs will more than offset the occasional trip.
It's kind of similar to why we got rid of the second car. Sure, it's useful, but for all the extra costs, I can take multiple taxi trips a year. (I barely do 1 in practice)
I mean it really depends. There are probably some circumstances where it's cheaper. But I think it's not a forgone conclusion. Renting costs money, and you'll need gas for it too. Motortrends estimates 1300 to 2000 a year in fuel for an Accord. And 400-1200 for electricity in a tesla model 3 (charging at home not a supercharger). I can easily imagine eating up the savings in one or two rental trips, and that's certainly less convenient.