I'm getting ever closer to forty and I've never taken a vacation and it has been at least a couple of years since I've even had a day off due to illness (and, then, only because I was so ill that I physically could not crawl out of bed). My boss has been prompting me for dates when I want to use my vacation for the last several years, because I've always been maxed-out, and I've been coming up with excuses and delays to not have to take the time away.
A lot of that has to do with work-ethic. I strongly adhere to the belief that a man's work is his legacy. It is his definition. More of it has to do with how much I enjoy my work. If my work were more of a chore than a joy, I would probably want to take vacations and would surely not hesitate to take a day or three off when sick.
It's the same way that some people talk about how they can't wait for their in-laws to go away when they're in-town and you never hear a word from other people. In-laws are only a problem if you don't like them or can't stand them. That isn't the case with everyone. Just like vacations and work.