It seems like the struggle for people in these jobs is mostly around the consistency in hours, and the miserly low pay. Both of which are deliberate choices by the firms that employ them.
To some degree, serving the "customer" by cutting labour costs to the bare minimum (as a way to minimize the cost of everything), means we create an awful existence for the people who depend on these jobs for a living. The tyranny of their lives is dictated by a consumer base who constantly demand lower prices and will shop elsewhere to save a dollar or two.
I worked in a supermarket for four years, but it was part time, while I was in High School and in my first year of University. I didn't need the money in the way someone working full time needed it. I was given consistent hours every week.
Working retail for a modest wage (say $25 an hour), with consistent hours would be a really great career for a huge swathe of the population. Lots of people (myself included) enjoy interacting with people all day.
A lot of more traditional professions have a better balance between physical work and mental work (skilled crafts, engineering in the traditional sense, or being a doctor all come to mind). Modern knowledge work doesn't have enough physical movement involved.
I wouldn't like to do it full time, but sometimes I wish I could spend 20% of my time doing something enjoyable but menial like stacking shelves. I think I'd hate doing it full time, but one day a week? Practically sounds like fun!