There are side-effects of PrEP for long-term use. It can cause kidney damage. So it's not an entirely risk-free magic pill.

It's still much safer to only have sex while in a monagamous relationship where you and your partner have been tested for HIV. And checking test results before having sex with someone is also a very safe practice that is really common. But in the end if you're often sleeping with people who you don't trust, PrEP can be worth the risk.