Appreciation seems to be contagious. Sometimes when people see others express appreciation, they realize they should too.
Both my parents spent a lot of time in the hospital before the passed away (not at the same time, B”H). I made many trips on the shuttle bus to and from the parking lot of the hospital. One day I realized I should thank the driver. So I did. Nobody else did.
Some weeks or months later, I noticed that nearly everybody was thanking the driver. It takes just one person to start a trend.