It only takes one accidental drop to make you regret that decision
Not if you have AppleCare+.
Personally I have had every iPhone each year since iPhone 3GS, never had a case or a screen protector, only smashed a phone once and had it replaced within a few days for a small fee and never had problems with their durability, especially the last few years they're so durable and have been dropped now and then without having a single mark on them.
I don't baby them either. I throw my phones onto tables, onto the sofa, chuck it in the space in the car beneath my dash after plugging it in when I get in to drive.
I am glad I've never been anxious about them personally or felt the need to put cases or protectors on them, and can use them as designed and intended - as a daily tool - without fear.