Because the government is now in front of a judge saying "your honor, this person is such a grave threat, that they must be imprisoned for 33 years." Anything less is insufficient. Yeah, its true that just a few months ago we thought this case was worth 7 years, but now we think its worth more than 4x the amount. There are no additional facts, btw, that would justify the departure. Everything we knew about the defendant's conduct, we knew when we offered 7. Had the defendant accepted the plea, the Gov would have found itself in front of the same judge, justifying why 7 years is an appropriate sentence on the case.
And LOL at you're use of "cooperate." Giving up a constitutional right, pleading guilty, and being sentenced to years in prison just so the gov't doesn't have to do their job is not what I would call cooperating.
Two days ago, a colleague lost a trial. The defendant was offered "time served" from the people prior to the trial. He maintained his innocence. A jury disagreed. The people are now asking for 3 years in prison. Is that fair? Is that justice? But this is a regular practice. I've begged clients not to take a deal bc I believe the defense was solid and they were innocent. But they had offers to plead for "time served" and knew the DA would be asking for multi-year prison sentences at trial if they lost. So they took the deal, got out of jail, and now have a felony on their record.
The entire concept is built around scaring people into pleading guilty, regardless of the state of the evidence; and, bottom line, you are punishing people for exercising a constitutional right.