The same thing goes when playing sports; we want a well known brand like Nike or Adidas. However, Nike and Adidas may not always be the best known name brand for the sport that you're playing or even the quality. For example, the main name brand for volleyball is Asics because the majority of their sells is towards volleyball. Asics seems to sponsor a lot of different schools since a lot prefer to buy their brand over others.
However, there are a lot of schools or teams that have Adidas volleyball uniforms though. This could be because of a money situation or the team or coach likes the look of the uniform better. As long as the uniform is comfortable it shouldn't matter what brand it is, at least to a kid because sometimes coaches get a discount through different companies. You should never complain on what kind of uniform you have because there will be teams out there that don't have as nice of uniforms that you do!
To go with your Adidas volleyball uniforms, you may want to try Adidas women's lima cool volleyball shoes or women's Adidas clima response volleyball shoes. It always looks nice to have the same brand of shoes as your uniform. And on that note I would recommend Asics, well at least their shoes.