Yes indeed kingston_toon, the larger amount the better the reward. Most folks don't get that far, or want to use them for short haul holidays. They may find they don't have enough to take the whole family, or that the taxes now charged overbalance the scales.
I recall some years ago cross checking Air Miles (the old UK BA scheme) and a direct pricing of the same BA flight LGW~AMS rtn. Buying direct was cheaper and it was cheaper still to use EZY, which we did. It was obvious that Air Miles had weighted the 'taxes and charges' to get more cash.
As is often said: Buy a long haul ticket in Economy, use miles to upgrade to a higher cabin - at the time of purchase.
There are web sites dedicated to people who go utterly bananas on this subject.