This is a fantastic article that asks the question, "Why let Green Lantern and Batman keep their continuities?"
When DC relaunched it's line under the 'New 52' banner last September, Batman and Green Lantern were the only two heroes that kept their relative history in-tact. Geoff Johns spent the past eight years rebuilding Green Lantern from the ground up, so rebooting him would be like slapping every fan in the face. Batman, on the other hand, is simply DC's most popular character, and one that has spawned so many tertiary-turned-main characters (Robin[s], Batgirl, Batwoman, Nightwing, Red Robin, etc.) that his history couldn't be re-written without sacrificing connections across the DC imprint.
Check it out over at Comic Book Resources.