I personally haven't worked in a restaurant, but I see how the staff and chefs are always running around, doing 20 things at once. Stimulants use like cocaine and amphetamine is endemic in the industry as well, probably for that reason.
As a restaurant worker, the pay is usually terrible as well. So while some super rich corporation won't lose millions off of your mistakes, you can lose your job and be forced to live off of your inexistent savings. That sounds very stressful to me.
Your assessment for what constitutes stress seems to be, at best, highly subjective.
For me, the cumulative stress of the software industry is a lot higher. I can never quite "turn off" and in the long-run it's a lot harder for me to control my psychological stress, than when I was working in a kitchen.
(And of course these are highly subjective, I'd expect nothing less from a psychological phenomenon. Anecdotes will likely be all over the place.)
For some people, server jobs are a between what they're doing. Especially for artists/filmmakers it's money between the gigs that don't pay. I met tons of people as a barista doing exactly that.
Worked through college, and yes conditions need to be better overall. A concern would be if it's now a FT 40h something or other, it squeezes out people who take 6 months making coffee to get to their next acting gig. Also, barista jobs are a dime a dozen once you make some friends. Very easy to get rehired, people talk.