Legitimacy from the perspective of the right of the government to incarcerate someone. Now that we don't have capital punishment, incarcerating someone is the most egregious thing that we allow governments to do to anyone.
In situations like these it is quite merited that the incarceration power be used. But when a certain point of time arises past the minimum sentence that we have in the law, it is important for the government to have to check in and see if it continues to serve the public and the state's interest to hold someone. In many cases it will. In some cases, however, it will not. I understand the victim's perspective, but justice is not being achieved if there is an individual who is no longer dangerous, who has served their debt, and despite the pain that it may cause to a family to have to go through a hearing, the individual really ought to be entitled to have that hearing, to have some objective person make a decision about whether they can rejoin society. That's why we would say we still need to have those hearings.