I remember, when I was a child, that we did use sunscreen when out on a bright summer''s day. Sunscreen with factor...4.
Then. later, there was 8. Then there was 16. From some point, you'd not see the factor 4 in the drugstore shelves anymore; instead, there was factor 20, 30, and then even 50.
It's not just that people are inside more, and thus need more protection when they are going outside. There's a need for more protection because there's more UV around. A recent study shows this very, very clearly, and the whole thing is freely accessible here in English. If you prefer German, here's an article in the Spiegel that's more or less a very short summary.