Old Key West was the first
DVC resort built. Disney had to decide the point schedule before they started to sell points.
It was only after OKW sales began that they realized they really could have set the points much higher for certain units. There's virtually nothing DVC can do to change the point schedule now at OKW, but subsequent resorts clearly have much higher values.
As a side note, be aware that there are only 26 Grand Villas at OKW. Members can begin booking 11 months in advance. These rooms are very much in demand due to the low point schedule you asked about. So, if you're looking to rent points for an OKW Grand Villa, I'd highly recommend starting to look for an OKW owner willing to rent enough points at LEAST a year ahead of time.