What are the benefits of the probation system?

Probation is a penalty that can benefit the community without overextending the system in terms of resources. 

Some benefits are giving the individual a second chance at becoming a law-abiding citizen and become contributive in society. 
Another benefit is to allow for the individual the opportunity to care for themselves and their families without becoming dependent on the state because those on probation are required to work and earn pay in order to care for themselves / families.

Hope this helps.