.That's not fair to assume. Different people have wildly different poracity in their enamel. You can be a health nut who brushes obsessively, forgoes all soda, and still gets cavities, or numbskull who does the bare minimum and is never punished. That's not to say oral hygiene isn't important, since for everyone in between you can improve your outcomes by taking better care of your teeth, but don't make the mistake of assuming that someone with shit teeth doesn't even try to take care of them