Christmas makes you depressed? Tell your family that and no longer celebrate it, simple, yes?
For everyone else (especially the ones with decent jobs or know how to save and don't go bankrupt from spending like $200 on presents once a year) you get 3 days paid holiday and an excuse to have a party and celebrate what's good in life with people you know and care about. What can go wrong?
There are religious reasons as well, of course.