User blog comment:ChiroSamai94/Brook the last crew member?/@comment-3060121-20120501153225/@comment-85.24.209.2-20120502163839

Bonehead Skipper@: Do we know the back story for all of the Sun pirates, Whitebeard pirates, Roger Pirates, Red Hair pirates?

No, because they are not main characters of this series, we are most likely only gonna get to know the backstory for the "important" ones (Roger, Shanks for example).

"Add members through time skips and just add them in with no formal introductions."

Thats not how it works, the Straw Hats are the central main characters of OP, every member is supposed to be important to the main story becuase its their journey thats is the focus of it all. And then there is things like charcter development, having something silly like 20+ members would take away all that, its bad enough there is already some few members in the crew who could need some right now (Sanji and Franky for example, they haven't done much lately).