The first poster obviously only has a superficial knowledge of DBZ. Anybody who actually watched the show would clearly remember that Krillin played an important (if secondary) role in almost all of the major battles.

He's delivered life-saving Sensu Beans to several characters at critical moments, used his Destructo Disc to slice off Frieza's tail, and helped track down Dragon Balls on multiple occasions!

And, of course, he landed himself a smokin' hot android wife.
( ͡° ͜ʖ ͡°)

Also, inadvertently caused Goku to super sayain.