I.... they are dealing with systemic poverty. Being poor is expensive. They absolutely know they need to save, but if the choice is "starve to death today but save for retirement OR don't die, but don't save for retirement" most people are going to choose the latter.
McDonald’s will not let you work 40 hours a week, or any consistent schedule at all. You will show up when they tell you to and that’s that. Same with grocery stores or most retail jobs.
Also you’re neglecting the cost of transportation (almost certainly a car, with gas and insurance), rent, and medical expenses.
Median rent value in Seattle is $2300/month if you are looking for a one bedroom, a little cheaper if you are looking at a studio. Minimum wage here is $21/hr. The first quartile for rent is $1600.
Assuming you work full time, you are making $3360 a month, less taxes.
That means that even if you get the bottom 25% of rents, over half your take home pay goes to rent. Then we need health care, food, taxes, transportation, clothing, etc.
Not a lot of savings easily available there.
I rent a room. But to be fair when I first came to Canada and was told by a local "of course you won't get to have a whole apartment all to yourself" my mind was blown away.
I just checked and McDonald's pays $15 an hour, no? That's more than enough to not starve.