Hey, don't go knocking CP+B. Their work for Domino's is top-notch, and their Volkswagen campaign remains some of my favorite advertising period. Meanwhile, while they've had the few early misfires for Microsoft, their work promoting Windows 7 was damn good, and they've done a lot for the Surface considering they don't have a whole lot to work with.
And the Groupon ads were hilarious. Terrible ads, and they should have expected the horrible PR they received, but they were among my favorite Superbowl advertisements to actually watch. More advertisers should be willing to risk PR flack in the service of making something memorable – CP+B's ratio of wins to losses is enormous, which is why they keep landing huge clients.
As for the "accept their creative without input", yeah, advertisers love to find clients willing to give them free range, because clients are often very good at fucking up smart ideas. They don't insist on that contract, though: Groupon's blog mentions that they "gave them a shot at pitching us concepts, and they came up with an idea we couldn’t resist blowing millions of dollars on." [https://blog.groupon.com/cities/groupon-super-bowl-ads/]