I honestly don't think one needs a screen protector but it's just added sense of comfort to those that need it for their OCD or something.... me included. I think over normal use a few very fine little scratches here and there is just normal wear and ok but I just hate to see it when the phone is new so I put one on.
My routine with phones would be brand new I get a screen protector and run with it for the first year and then once the newness wears off I usually end up taking off the protector, admire the difference in look and feel and go naked with it for the remainder of my ownership... another year or so. And when I look at all the devices I've had... not a single scratch. Maybe a few superfine ones if I really have to look?? And I'm probably babying less during that time then I did the first year. I look at all the iPads I've had over the years never having a protector and nothing either.
My wife she hates protectors even tempered on her iPhones... tried putting one on her 10 then 11 Pro and she just took it off. She plays beach volleyball a few times a month so she'll get sand all over her stuff and me I'd go nuts if there was one grain near my screen but she just wipes off and looks fine. If I look closely I may find super super fine ones but she doesn't care. Her Apple Watch too. More power to her.
Now if you are a clumsy person, then maybe more for avoiding cracks. Since the iPhone1, I can probably count with one, may both my hands, the times I've dropped my phone. But never cracked or killed a phone so I don't buy protectors for that reason.
My daughter has never cracked any of her phones either, but she's dropped her phone in front of me for no reason more times I care to remember. So when her iPhone 12 Pro came in yesterday, I put the Spigen glass on it the moment I took off the plastic film off the screen and gave it to her as her belated grad present. She doesn't care about scratches either but she accepts it to humor me lol.