Why would a character permanently join a crew?

As a story teller, the concept of crews, adventuring parties, or bands of heroes is a staple of epic fantasy. However, I'm curious about what would motivate a character to permanently join a crew and forsake other parts of their lives? For example, a traveler may run into a local lord who is a great leader and defender, but would an adventuring party choose to be their vassal? A person might save a kingdom from a great threat, but would they join the kingdom's military? A pirate captain might have a code of honor and protect the vulnerable, but what would motivate someone other than a pirate to join their crew?<br><br>It's a foolish thing to say that a person's motivations can be boiled down to just one thing, but I'm looking for a few different reasons why someone would want to remain with a crew for the rest of their life. I'm curious about the legal, social, economical, and political reasons why someone would want to remain with a crew for the rest of their life.<br><br>It's a character's motivations that really make their decisions and define them as a character.