What is dis advantage of Human Machine Interface?

There really aren't any disadvantages of an HMI. Typically, HMIs are used in factories, manufacturing process lines, and actually places like Sheetz to order food. HMIs have greatly advanced efficiency & safety in manufacturing. A worker will input, or enter data on a screen and an automated process could function for an entire shift without human involvement. The only disadvantage would be; 'there aren't enough choices on the screen', for ex. You might want a hamburger cooked 'medium' instead of well done.