Because thats not correct. The Mac Box set is licensed for Tiger users. If your computer has Leopard (via having a retail discs or restore discs) even if it doesnt ask you, is sufficient - its an honor based system. Apple is just asking that you have the previous system somehow. Every retail OS has been able to be installed on a blank hard drive, but that isnt unique to Apple - you can install Windows 7 Upgrade on a blank hard drive (MS is bigger on enforcement however).Fair enough but if I can pay Apple 29 bucks for a upgrade disk to take me from Leopard to Snow, then im slightly perplexed why they tell me i need to shell out over a 100 to do a fresh install.. Dont see why i should pay all that amount more to do a fresh install on the same machine..