I am one of the people who wear a mask while driving alone, usually to go to the grocery store, when I leave my apartment I put it on in case I run into anyone on the way to the car, I'm not about to take it off once I get in my car and risk spreading it inside so it stays on,
then after the grocery story I have to walk back to my apartment and risk meeting people so it doesn't make sense at any point to take it off until I am in a safe spot where I can wash my hands