When I worked a more active job, I used them religiously. I thoroughly tested OtterBox's warranty.
Now that I work a desk job, I'm much less worried about breaking my phones. I put a skin on them for the aesthetics and improved grip. Over 4 years case-free on 4 phones, zero issues.
Never had a case for my phone. And in 13 years of owning a smart phone, I only had a single broken screen this summer. And in that case, a phone case wouldn't have helped protect it.
It's really not hard to not drop it is you're careful.