It feels good to show people how much you appreciate them, especially if they’re doing some type of work for you. When people feel appreciated, they tend to enjoy their job more and are more likely to do an even better job than expected. Being nice is nice.
One neighbor was having work done on their house and felt bad for the guys working on a Saturday. So, she decided to show her gratitude for their hard work with a box of donuts and a cooler full of water. The guys working on the house probably really appreciated the gesture and enjoyed the refreshments.