To many people, including probably most on SAS, being a janitor is a far more promising option than being a cashier, working long lines of impatient people (frightening for us, stressful for anyone, and mindnumbingly tedious) a good number of which snarl at you about discounts, talk loudly on cell phones, treat you as subhuman, etc.
I've done both jobs and I would gladly take the role of janitor. You get to zone out, listen to music, and not deal with annoying people.
As for the pay, you can make 15-20+ an hour as a janitor at an institution. As a cleaner, I make considerably less, but significantly more than a cashier, which is typically minimum wage or just slightly above.
And I always take pride in my work, no matter what the job is.