Here's why:
* Legacy: Solomon Muto, Yugi's grandfather, was a renowned duelist known for his powerful Dark Magician deck. When Solomon passed away, he left his deck, including the iconic Dark Magician card, to Yugi. This card became a way for Yugi to remember and honor his grandfather's legacy.
* Special Bond: The Dark Magician is a powerful and loyal magician, much like Solomon himself. Yugi feels a deep connection to the card, seeing it as a representation of his grandfather's spirit and guidance.
* Spiritual Connection: While not explicitly stated, there's a strong implication that Solomon's spirit resides within the Dark Magician card, guiding Yugi in his duels and battles.
* Strength and Determination: The Dark Magician embodies the strength and determination that Yugi inherited from Solomon. It's a symbol of his resilience and his ability to overcome challenges.
In essence, Yugi's Dark Magician isn't just a card; it's a symbol of his legacy, his connection to his grandfather, and his own strength as a duelist.