Running out of product keys??? (Score 1)

Has anyone done the math? Running out of product keys is NOT the reason. The product key is 25 characters long and contains uppercase letters and digits. If, for arguments sake, 20 characters are real, and the last 5 are 'check characters', then this allows 36 ^ 20 possible combinations. This is 1.3E+31. This is enough for every person on earth to have a billion billion keys. If there are only 15 unique characters, with 10 'check characters', then this is 36 ^ 15 which is 2.2E+23. Or every person on earth could have about 3000 billion keys. I dont know what Micro$oft's real motive is here, but running out of keys is NOT it!!