Do they?
How would you know that?
Mrs H is a good example - she runs an Alfa 156 Sportwagon, but has only done a single journey in the last 12 months that couldn't have been covered in a Leaf, for example.
Now, I'm not saying she should go and buy a Leaf, and she wouldn't, as she's a bit of a petrol head - but there are many more people out there who work just a few miles from home and / or only do a short school and shopping run who could quite easily have an EV only car.