I enjoyed that what I did made a real impact on people, I enjoyed the sense of satisfaction from making a space nice again, and I enjoyed that it wasn't intellectually demanding, which gave me plenty of time every workday to think about hard programming problems.

There's a real sense of accomplishment in it, and it's nice that people can immediately see and enjoy the results of your hard work. There's also something about doing manual labor that is satisfying.

And I enjoyed being "invisible" around people who used the spaces I cleaned. You usually don't exist, so people tend to continue to speak to each other as if nobody else is listening. I learned a lot about people that way.