Why don't I see other characters in the Mos Eisley Cantina?
They had better things to do.
Eragon, Arya, Saphira, Nasuada, Roran, Katrina, Murtagh, Thorn, Orik, Galbatorix, and Sloan. Those are the Main characters there are other characters but these are discussed throughout the book. The "detail characters" are the characters where they appear in one or two scenes and dont come back in the story. (detail characters also dont have a Big impact on the story)
In Naruto Ultimate Ninja Storm is it possible to not use support characters in battle when you dont want them?
Think of Tom and Jerry. They dont speak either. Garu and Pucca dont speak becuase they use movements and small sounds like grunts, sniffs, etc. Also, when they dont speak, it makes them unique from all the other characters. However, there is 1 eisode that i know where Pucca and Garu sing. If you would like to watch you can go on youtube and search, "pucca bollywood episode" or "pucca bollywood song" Hope this helped!