I've never used a screen protector on any of the many phones & tablets I've owned over the years and have never had a problem with scratching. I always use a case, though.
Never used a screen protector on any of the 6 iPads we've had in the family. No noticeable scratches even though we've used nothing but smartcovers on the ones we've had over the last few years. (The original iPads got folio style covers, but nowadays we take the weight side of the protection vs weight trade-off.)
Then again, I'm on my fifth iPhone model and only one of those ever had a screen scratch. I'm not super careful with devices, but neither am I particularly hard on them.
Screen protector is a little investment that will actually goes a long way... I do have them and it keep me worry free. I'm quite OC so can't live my devices naked..
Screen protector gives me piece of mind when chucking the iPad in my bag. Also, I find the feel of screen protectors more pleasant than glass. Feels smoother and less grippy. Also, you can get some that reduce glare in case you use your iPad outside.
Screen protector gives me piece of mind when chucking the iPad in my bag. Also, I find the feel of screen protectors more pleasant than glass. Feels smoother and less grippy. Also, you can get some that reduce glare in case you use your iPad outside.