I didn't for my S8+ and regretted it, in my line of work I need protection and I scratched the screen pretty bad on hardened joint compound, could never un-see it at that point, there was a physical lip on the scratch. My S9+ I got a case that has a built in protector and my phone is mint a year later plus it has been dropped a lot and so far so good. So I'm really glad they're including one from the factory, now I can finally order a case and not worry.