For me, it's for collection purposes. The original cover of Kingdom Hearts and Star Ocean: Till the end of Time and the greatest hits version of those two games are great examples. Other times, in the case of Grand Theft Auto: San Andreas and the Hot Coffee mod, its hidden content thats only available in the original print. However, there are examples where the Greatest Hits version of the game is superior to the original release. Devil May Cry 3: Special Edition, Silent Hill 2 (has the bonus content from the Xbox version), and Virtua Fighter 4: Evolution are good examples of this.