If you are offered a plea agreement you had probably best accept it. Prosecutor's careers are determined by the number of cases they successfully close without 'giving away the farm.' If they are too...
If you are charged with a crime - SOMETIMES - in order to save you from a conviction for a serious offense, AND to save the government the cost of a trial - OR - in exchange for needed information...
The prosecutor's motivation for a plea is just to get the person in prison. If the defendent pleas guilty for a plea bargain the prosecutor has won the case and accomplished his goal in succeeding...