Same, I have owned the 5, 6, 7 Plus, and X and I have gone without a screen protector. Only protection on my iPhones have been the Otterbox Symmetry line of cases (and Commuter before Symmetry series were produced).
Have I had hairline scratches on my display that are barely visible and only in direct sunlight? Yeah. Does it bother me or affect my resale value? Not really.
Being someone who has OCD-like tendencies, the first scratches are always the worst. After that, the feeling fades away.
I used to scoff at screen protectors, until I started noticing fine scratches in the glass of my iPhones. It really bothered me. So ever since my iPhone 6S Plus I have used them. A few pieces of tape and a squeegie is all you need to achieve a perfect, bubble-free installation.