In general, getting elderly people, low-income populations and other late adopters of technology to use touchscreens correctly has been much easier than getting people to use a mouse. The mouse is less physically intuitive than "poke the thing you want." For most of us, though, we hardly notice a difference.
- since there's only one screen, and it's all touchscreen, users get consistently confused between pictures of buttons describing what the buttons do and the buttons themselves
- the touchscreen is itself a peripheral and prone to wearing out. When it does, the fact it's wearing out is difficult to observe during the election day; there's no cursor indicator, so a poll worker can't check calibration.
- users with fine-motor-coordination issues have to brace against the box to steady themselves to touch the tiny targets they want. There's nowhere to brace against a touchscreen that isn't also touch-sensitive input, and the screens don't accept multi-touch.
A row of buttons along each side of the screen, not unlike the solution used at many ATMs, would ameliorate all these problems. These boxes are already custom hardware jobs, so switching out touchscreens for a couple of button banks would be cheaper, equally usable for most voters, and more usable for mobility-impaired voters. It would improve all three observed problems.
Wishes and horses though; the machines we have are the ones we use.
People consistently overestimate the reliability of that solution, especially for older voters with mobility challenges. Pushbuttons or levers that demand macroscopic elbow/shoulder motion are easier for that demographic to use than sensitive screens requiring fine motor control.
And that's all to say nothing of what happens when the screens become miscalibrated and accept taps a few pixels off. I'm fairly confident most of the "It switched my vote" reports we hear are actually this category of "user-error" (which should really be counted as "machine malfunction").