Is it any wonder that people treat such workers like they're sub-human? After all, most places make you memorize or repeat the same robotic lines for every customer, have you all dress the same, and in most service jobs these days you're either hidden behind a counter, plastic shields, masks, and maybe hats depending on where you work. Of course there's a very good reason for masks, but hiding your face has an unfortunate social effect of making someone appear suspicious regardless. Face to face contact and honest conversation is often impossible and discouraged in exchange for better work efficiency.
Workers are dehumanized by customers because they're dehumanized by companies and higher staff. That's why I think most Karens treat service workers like a busted toaster that you have to smack to get the toast out or something. Corporate phrases like “the customer is always right” feeds into their egos, so they feel cheated if they can't always get exactly what they want, or if the person they're buying from makes a small error. They feel like they should expect the absolute perfection that a company unrealistically advertises and forget that the people making their meals or doing jobs for them are real fellow humans who make mistakes like everyone else.
In short, I think everyone needs to be reminded that you could be talking to a great person, someone's friends or family, or maybe a person who has been having a tough time lately, or maybe just a person who wants to get home and eat and sleep like everybody else. We need more compassion for workers and to better recognize and call out these corporate lies and tricks until we change the system and hopefully find a better way.
TLDR: Companies dehumanize workers, so is it any wonder customers so often dehumanize them too? Let's be nicer to each other.