The sentencing guidelines say they do.
In a way it's the other way round: in deciding on sentence, the judge has to take into account aggravating factors, which include the severity of the crime, the vulnerability of the victim, and the history of the defendant. So if the defendant has a history of previous offences, that will increase the sentence. When you are working to a maximum of 12 years, that is the sentence that would be passed for a crime at the most severe end, involving the most vulnerable victim, and for an offender with a very bad previous history. So if one or more of those aggravating factors isn't present, the sentence has to be reduced accordingly.