By forcing me to only get the money if I use it for vacation, I will have a better time, and I will relax more, both of which will improve my stress levels, etc. Also, the fact that they are pushing this into their culture shows that they truly value some sense of work/life balance, which is a big turn on for a company. So many companies say they want work/life balance, then you see that working <60hr weeks is seen as not pulling your weight.