@Mielly I never once said cleaning floors was fun, I said retirement can be boring. However perhaps being around people is better then lazing around in a house possibly all by yourself waiting to die. You might not exactly have many close friends at that age, and it may feel better to be around others, even if you're laboring.
As for your second point, im not sure what that has to do with anything my comment said, that's cool and all, but still what would you want this 75 year old lady to be doing if she is gonna work in this company? I get you're implying you can go up from janitor to other jobs with time but we don't know anything about this lady, how long she's worked here, how long she's worked in general(perhaps she was a housewife most of her life) or if she even wants to "move up"
your last point is something I have no problems with, but people are allowed to do whatever they want, my grandpa could easily retire at this point, but continues to work because he likes working, even though it isn't the best/high paying, etc... Once again we have no idea why this lady is here, I guess from your POV you think its a hellhole because she's doing this to survive but we don't know that, as, like I said, some people just like working