A lot of people are quite happy working, quite happy with their local environment, and feel no need to take a vacation. For other uses of (paid or unpaid) days off (being sick, funerals, important kid events, 'just not feeling it today', maternal leave, paternal leave, whatever) policies vary so much from company to company and individual to individual; I think this variability is a good thing and gives an additional dimension for companies to compete for workers on.