Be honest: when you reach for a physical button you might glance for 0.5 seconds or even less. Usually you'll try to reach it without looking, and only glance if for some reason you can't do it. You glance, reposition your hand, and operate the knob without looking.
When you try to use a touch screen, you look at it all the time. I've just tested: to unlock my phone I have to push a physical button on the right side, swipe up and then make an easy pattern. I can grab the mobile, orient it correctly and push the side button without looking or even thinking. But just to make the up swipe I look at the screen (I can force my self to not do it, with effort). But I'm unable to make the pattern without looking all the time I trace it. It's like the brain don't want or can create muscle memory for touch screens.
When you try to use a touch screen, you look at it all the time. I've just tested: to unlock my phone I have to push a physical button on the right side, swipe up and then make an easy pattern. I can grab the mobile, orient it correctly and push the side button without looking or even thinking. But just to make the up swipe I look at the screen (I can force my self to not do it, with effort). But I'm unable to make the pattern without looking all the time I trace it. It's like the brain don't want or can create muscle memory for touch screens.