Because they didn’t do anything wrong.
What serious candidate for POTUS on the eve of two primaries goes home and skips planned meeting in those two states?
That simply screams the candidate is giving up.
The Cruz camp didn’t do anything ethically or morally wrong.
The Carson camp screwed up and sent out a message that would only be taken one way.
There weren’t any planned meetings in NH or SC that I could see on Carson’s official campaign website as of this morning. There were no campaign events listed for ANYWHERE.
Which would be awfully strange for somebody who wasn’t throwing in the towel.