Why won’t Randy be at the fight between the two gangs?

Randy Adderson, Marcia's boyfriend and Bob's best friend, chooses not to be at the fight that occurs between the two gangs. His absence from this brawl is significantly linked to his friendship with Bob. Bob, as you may remember, was stabbed by Johnny in the park. Randy leaves Bob behind and this is a critical moment for Randy's character—this moment has a significant impact on his views and thus contributes heavily to his decision not to fight.
Keeping this key moment in mind, one can explore Randy's motivations. He watched his best friend be stabbed to death in a park after he and his other Soc friends drunkenly antagonized Ponyboy and Johnn—all because they were from a rival gang, a group of boys leading a different lifestyle from their own.
The impact of this left a lasting impression on Randy. He seeks Ponyboy out to talk. He confesses his confusion about this pointless social battle. He is sick of the fighting and the horrendous outcomes that he has witnessed.
Although a minor character in the novel, Randy allows the reader to explore the Socs in a much more humanistic way than we often see from other Soc members. Here is a teenager who witnessed his friend die and does not find closure in continuing this fight. For Randy, this conflict is meaningless, and he wants no part of the brutality, so he separates himself from the violence.