You shouldn't constantly be hovering over your kids. Still, you don't want them to get in serious trouble. As a parent, you can curate the options they have without knowing exactly what they are doing. You can fill bookshelves with appropriate books, and if you see them reading on the couch, you don't need to know exactly what they're reading. Some people also are able to control where they live, what schools their kids go to, what friends you invite over to your house, etc.

One day your kid might have the friend over that you suspect might be trouble. You check in a little more often. Online is harder. You see them with the device, and without controls, what's going on could be almost anything.