In a Lot of Situation, at least in the UnitedStates one reason for Plea Bargains are most, not all but most Jail & State Prisons ar SOOO over crowed they PLea bargain the lmits thier time behind Bars
Look at Conrad Murray, he got 4 years for the "Involunatery" death of Michael Jackson, as as soon as the sentence was passed, before he even left the court room EVERY Memembero f the Media and even those in Charge of the California Peenal system said "He wil serve very limitedtime, we have a MAJOR or crowding situation State wide and need to leave frooom for the most Violent Offenders etc
Nation Wide most Prisones are over crowned I firmly believe because of this those who are convicted of Some Crimes simply serva limited ammount of time
Also keep in mind in California the Charges that Murray was Convited of only carry a MAX Sentence of 4 years, the Judge wanted a stiffer sentence ubt he even admitted he is bound by the Laws of the State as well as the over crowding if their Penal Sysem
That is why unless the Case is Horrific in Nautre, PLea Bargain wil always be offerd, plus those covicted gnenera lwork under soneone elses order, the JUsge wants THAT person not the Messenger so to speak