That's not by accident. Exclusive partners gain that status by agreeing to help subsidize the product in some way, shape, or form. And they want their money's worth, so they (the partner) make sure the contract lasts just long enough for you to not care after the contract ends. Of course, the first party is hoping the product catches on, is insanely popular, and continues to drive demand after the contract is up. That doesn't always happen.
So, it's a catch-22. Do you as a first party go it alone, and incur more cost, or curtail your retail spread and take less of a hit up front? From the disinterest in the retail Chromebooks, Google made the right call there.
That said, I wouldn't have minded a CR-48... But it was a little costly, and the other models were a little too wimpy. I'd think Google would take a risk by taking a loss on one huge product push... But I guess not.