Here's why:
* The Member Card is used in the Diamond and Pearl games for specific features like discounts and access to certain areas. For example, you can get a discount on items at the Veilstone Department Store by presenting your member card.
* Pearl does not have these features. While there might be some places that require a membership in Pearl, they won't use the Member Card system like in Diamond.
If you are playing Pokémon Pearl, you don't need to worry about a Member Card. Focus on enjoying the game and catching all the awesome Pokémon!