Greasers also known as hoods, was a subculture that developed in the 1950s. Their icons were Marlon Brando and James Dean. They were known for their sweet rides such as hot rods. The name Greasers came from their hair style. It was combed back with wax or gel.
Teenagers might want to join a gang because it's cool and their friends are doing it. They'd also get the three R's- respect from others, reputation- for committing a crime they feel powerful and having the best juice (rank) and they would have revenge.