I don't understand how a company is supposed to combat this. It's just accepting reality that "there will be underage users on our site anyway, and there isn't

I don't understand how a company is supposed to combat this. It's just accepting reality that "there will be underage users on our site anyway, and there isn't anything we can do about that, because they will lie". On a case-by-case basis if you find out someone is underage you have to terminate their account, but by and large you just have to accept that these people exist. Many of my online accounts were first registered when I was underage. I'm not eager to let them know that, of course.