As a Stock Aesop, believing in the Power of Friendship over isolationist self-reliance is pretty standard and true. There's a lot a group can accomplish that the individual(s) acting on their own can't. In fiction, Friendship even brings tangible benefits like a Five-Man Band developing an Attack Pattern Alpha which uses All Your Colors Combined. Some shows may even go the extra length to crush the message into a viewer by having a Sixth Ranger fail miserably and join the team. Once the Season Finale rolls around however, The Hero can't depend on his weak friends to keep up, and will have to fight the Big Bad Final Boss on their own.