If you wanna decide to use a screenprotector or not depends on what condition you want your phone to be in after some time of use.
If you want no hairline scratches then use a screen protector! That theyre not nessecary anymore is absolute rubbish, unless you dont care about minor and even major scratches.
If you tend to drop your phone i would recommend a case, unless you dont want bumps and scratches on your phone.
If you dont care how your phone looks, go ahead, throw it around and then keep telling it feels better naked, without screenprotector and case, while its horribly scratched and bruised. (like some extra smart people keep telling)