If you spend most of your time outside simply driving to and from work, you might not think sunscreen is that big a deal for you.
A study at St. Louis University looked at sun exposure from inside a car. They found that more skin lesions and wrinkles appear on the left side of people's faces, the side that is exposed as you drive.
While some windows in homes and cars do have tinting that filters out dangerous UVA rays, not all of them do. So, the study says the solution is simple. This is just one more reason to use sunscreen every day whether you expect to spend time outside or not.