People like to feel safe. Here the cleaning service has access to a business or a family's valuables. The cleaner has to value honesty or they will soon lose jobs and their good reputation.
I recently found $180 cash in a money clip at an office I was cleaning. I was offered a reward for turning it in which I turned down. Now the whole office is talking about me and everyone feels safe! This is of the utmost value to me!!
Your reputation is everything. That's how you gain customers!