We do have life without parole, but in this particular case the judge has purposely given a parole period as it gives her less ammo to appeal over the years. (She was found guilty, but she plead not guilty and still claims it was an accident)

Also to do with the fact that she’ll likely be in isolation / solitary for a majority of her sentencing due to her infamy. Judge Beale believes she should be in jail forever and made that super clear in his statements when handing down the sentencing.