Here's why:
* Bardock's story: Bardock's story is primarily focused on his past as Goku's father, explored in movies and specials, rather than the main Z timeline.
* Game mechanics: In most Dragon Ball Z games, the playable characters are those who prominently feature in the main storyline.
How to play as Bardock:
* Spin-off games: Some spin-off Dragon Ball Z games like Dragon Ball Z: Budokai Tenkaichi 3 and Dragon Ball Xenoverse feature Bardock as a playable character.
* Mods: Some fans create mods for games like Dragon Ball Z: Budokai 3 that allow you to play as Bardock.
* Fighting games: Bardock is a playable character in various fighting games like Dragon Ball FighterZ.
Remember to check the specific game you're playing for any available options to unlock or access Bardock.