I wouldn't say that PPF is necessary at all. It's a car - a depreciating asset that will get damaged by rocks, salt, etc. as you drive it. You can choose to care for the paint (or not) in any way that suits your lifestyle and budget.
I got full satin PPF on my MYLR. I kept my last car for 17 years and plan to keep the MYLR for a long time as well and I wanted to preserve the factory paint job. I know a lot of people say that it's just cheaper to repaint the whole car, but I wouldn't pay that amount to repaint a car after it's >5 years old (the timeframe when the paint damage may be enough to merit it). For the amount of money PPF costs, it makes more sense to me to be preventative rather than focus on fixing an even older, depreciated asset.
Plus my MYLR is black, as my last car was. It's a difficult color to keep looking nice and PPF makes that job easy for me.
Satin PPF has also been a bit of a wish for me. The first time I test drove a Tesla about 9 years ago, I saw another one there with satin PPF and I loved the way it looked. So I decided to go for it with the Model Y. It was very expensive but I'm fortunate to be in a place where it didn't compromise my retirement or other savings goals. And it's made me extremely happy. So it's been totally worth it for me.
With that said, if you're looking for some basic protection to avoid the worst of the damage that's inevitable, I'd suggest gloss PPF for the front bumper, hood, and the lower part of the rear doors right in front of the wheels. That seems to be a good compromise between price and protection from what I've heard from others.