This isn’t a scientific study but observations made over the last six months or so. I have become increasingly aware of the number of parked vehicles with engine running and a driver sitting inside.
These are not momentary stops, but over enough time for me to make a store purchase and return to my vehicle and continue errands. The conclusion I have come to is that vehicle fuel is still inexpensive, or there are people with enough expendable income that burning fuel and going nowhere is not a personal concern.
Producing unnecessary GHG emissions is another issue, but perhaps not a personal problem for that same group. A more thorough study is obviously needed.