As a Manager of a sports team, I've realised a few things,
GTA III had 100% completion, but there was no reward for doing so. Hence, it was largely pointless. By comparison, GTA Vice City has 100% completion as well, but it also offers an incentive to do so.
This type of gameplay doesn't appeal to most casual players, but it does make the game seem more interesting to hardcore fans. If they bother to 100% GTA Vice City, they will unlock.
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