What a terrible lot of cynics we have on here. Someone doesn't take their full holidays per year so the first thought is they must be commiting some sort of fraud! Dear oh dear.
For what it's worth, I don't take my full holidays in a year, though since marrying and having a family I get a lot closer to it than I used to. I can think of at least two other staff in our office who don't get anywhere near taking them all either. I'm not committing any frauds, and I'm pretty sure neither of the other two are either. I even worked Christmas Day morning once because I wanted to finish something before we came back from the Xmas break, though that was long before wife and kids came along.
Perhaps he just doesn't have anything better to do?