It's obvious when you think about it. They took an everyday task with 2 process options, the more expensive and less healthy one, involving zero participant involvement then in 97% selection. They engineered the possibility of mentally engaging "fun" into the alternative, thereby retaining and even improving the health positive effect and positive cost factors of that option and viola, most chose to have the fun it offered. The fun introduced the possibility of distraction from the mind-numbing sequence of all of those tasks we must all endure to get by in the world. Improved societal mental and physical health would follow more universal application of this type of approach to public facilities engineering.