I use one, but the feel of the glass without one is much better, so I understand those that don't want one.
Glass feels like glass to me, I personally don’t see or feel a difference.
Your advice may be relevant to you but not to everybody else. The screen protector on my iPhone 12 has quite a few scratches on it and a deep gouge. That sort of proves your point as being false in my case and the protector cost just £3.50 from Amazon by Spigen. Hardly a waste of money.Started with iPhone 4s. Never used a screen protector through iPhone 12. Never "babied" any iPhone model. And never, ever had any screen or scratch issue. And I regularly clean the iPhone screen with paper toweles and glass cleaner.
iPhone glass is robust. You simply do NOT need a screen protector. Also, you are wasting your money by purchasing them. You'll never recoup the cost of screen protectors with your perceived increase in trade-in value, which is nonexistent.
I say again, you do not need a screen protector. Waste of time, waste of money.