Hopefully if you're not going on your trip, you would cancel it before you were to leave anyway.
One would think that people would do that, but alas, not all do.
Hilton discovered this same problem with award reservations and changed their policies because of it. It used to be possible up until about 2 years ago, to make an award reservation even if one didn't have all the points in one's account. However, now Hilton requires that one have all the needed points in one's account and failure to cancel will result in the loss of those points. Apparently they had too many people booking reservations on hold like that, providing a bad credit card, no showing, and never cancelling. That of course left the hotel holding an empty room for which they couldn't and wouldn't get paid for. With a bad CC number and not enough points in the member's account, they had no recourse.
So now, one must provide a valid CC (they test it) and one has to have enough points to book the reservation and those points are removed from your balance at the time of booking. Only cancellation will get you those points back.