I have owned every iPad from the very 1st one. I have never put a screen protector on any of them, and have never so much as scratched the screen on any of them. And I've dropped a couple too! For me, I just cover the front and back of my iPad. I use to use Smart Cases, now I use either the Apple Smart Keyboard or the Smart Cover to cover the front, and the Apple Silicone Case or a third party Clear Case to cover the back. That has been fine for me. I've only dropped my iPad a couple of times in my lifetime, and it's been fine. Never while moving or outside. I just don't drop my iPads for some reason.
Now my iPhones? That's a different story. I put a screen protector on those as I use them in more mobile circumstances than my iPad. They're smaller and easier to mishandle or forget they're in your lap. I use them at the Gym, while running, etc. I feel it's more useful on my iPhone. But iPad? Never LOL.