SINCE WORLD AIDS DAY IS ABOUT PREVENTION

I have a World Aids Day question. Many of my friends get regularly tested for HIV which I don't understand. I know there are benefits to early detection. On the other hand, if you get tested regularly, you must be regularly having unsafe sex. Shouldn't a negative test result lead to vigilant safe sex so that regular tests aren't needed? Are we in denial if we know how to stop it and don't?