Parole can be a useful tool in corrections, both for reducing the cost of incarcerating inmates and for helping ease them back into society. The conditional nature of the release can encourage good behavior while behind bars and a constructive attitude toward life once released under supervision.
Parole's most direct benefit is to relieve prison overcrowding and ease pressure on budgets. Full-time incarceration is expensive, especially in high security environments, and many facilities are already overcrowded. Parole offers prisoners a path to an early release, conditional on good behavior, and allows the administration to choose inmates least likely to re-offend or become a threat to society for this program. Those prisoners who do the most to earn parole are likely to work hard once outside prison walls to maintain their good behavior, preventing reincarceration.
Parole can also be seen as an intermediate step between incarceration and release. Inmates who spend years in prison can find adjusting to life on the outside difficult, making it more likely that they have difficulties reintegrating into society. Parole requires regular check-ins with correction officers, and when paired with programs designed to help parolees get their lives back on track, it can be a way of guiding an offender gently back into society.