James,
My guess would be the British education system, but then I guess ours must be as bad, since I didn't notice I'd only played 17.
If Beau Desert only had 16 holes, it would still be worth playing. It's a knockout location, one of the best conditioned courses in the UK, and a great mix of outright star quality holes like 2, 5,7,9,10,12 and 13, and some like 6 that are more subtle, but nevertheless quite tricky, which is a bonus, because once you've been had, you can quickly nip back up the fairway and hit another second shot to try and make amends, since the course doesn't appear to be that busy.
Not that I would advocate that sort of behaviour, of course.