The issue isn't really that we roll to determine if we can damage an enemy, but that it's defined as a "to hit" roll in the first place. If I have a Dex of 8 and am wearing plate armor, when you attack, almost assuredly you hit something.
What you're actually rolling for is to see if you meaningfully bypassed my defenses. That's why Strength adds to hit, despite the fact that it doesn't seem to make any sense on it's face.
It's a pretty arbitrary system, overall, Armor Class and Hit Points, neither of which precisely mean what you might think they mean, but are an aggregate of a lot of factors. This ambiguity allows you to describe the resolution of attacks and the subsequent hit point loss in a wide variety of ways.
Maybe your attack penetrated my armor and now I have a vicious wound. Or maybe you slammed into me and knocked the wind out of me momentarily, and I can fight on. Maybe you struck my armor, but I turned at the right moment and the attack veered off. Or maybe you really did miss (but this isn't the default result, despite the terminology used)!