Thick skin is less sensitive.
Humanity has fairly acute senses of touch and vision compared to much of the animal kingdom. While we may lack the practically telescopic vision of an eagle or the night vision of a cat, we do have excellent color vision, depth perception that many herbivores lack, and a wider field of vision than most predators.
As we humans rely so heavily on our dexterity, a good sense of touch is a must. Touch is how we interact with the world, and (to an extent) how it interacts with us. It allows us to feel things that may cause us injury and react appropriately before we get hurt; reach towards a hot stove slowly and I guarantee it will be uncomfortable long before you smell sizzling flesh. If you had the hide of an elephant, you’d get horribly burned before you felt a thing. Okay, now put on a set of welding gloves and try to write… or even pick up a pen/pencil.
Of course, there are trade-offs. Our sense of smell is sup-par, our hearing rather less sensitive than many animals, and our skin pays for that sensitivity by being easier to damage (or rather, injure; it’s technically an organ). But our sense of touch allows us to to the whole tool-making thing far better than a more ham-fisted species of equal intelligence probably could.