You don't need to wear a mask by yourself in your car anymore, btw.

I've had a couple times where I simply forgot to take a mask off when I didn't need to wear it any more, and that includes driving in my car by myself. Others have told me the same thing. It wasn't because I felt I needed protection. I was simply thinking of other things and forgot. Have you ever done a stupid or embarrassing thing because you were thinking of something else at the time? Maybe you haven't. But most of us have.

Also: let's say you're on the way to pick up a friend of yours who has a compromised immune system and is at high risk. You're going to be giving them a ride somewhere, and droplets from your breathing prior to the person entering the car could still be in the air when they enter your car, and could infect them. Would you wear a mask even when driving by yourself in order to play it safe and protect your friend from that danger? Many people would. It's not just about protecting yourself. It's also about protecting others.