They aren't typically touch screen. But actually, a simple LCD screen is very easy and simple to do. The displays are modular and easily replaced. All functions are monitored and controlled elsewhere. I mean, think, though of the intense use and handling a phone gets. It will last. Usually the death nail for a phone (besides nefarious updates) is dropping and cracking the screen, or the battery. Neither of which would typically happen to a protected screen behind a flip down cover or a pop in plastic guard over the screen. Digital lcd screens can quite easily be made water proof as well.
What you are probably not understanding about the issue is the welder industry has transitioned to digitally controlled technology. When compared to analog technology of even just 10 years ago with many manufacturers, digital technology has reduced the sheer number of circuits and discreet components. Less circuitry means over all better reliability. On all of Everlast machines, most, if not all the main components are modular and plug and play. They are about 30% lighter than before on some products. If you think back to the early days of the computer (Univac), these were analog computers, taking up entire floors of buildings to do simple operations. Today, a simple cell phone has more than enough capacity to guide a rocket ship to the moon. Digitalization has made things more dependable in many respects, and not less dependable. Now, if you are dealing with cheap electronics, or poor quality control, in any system, analog or digital, it may make one system to be better than the other.