In my view, any "benefit" largely depends on your initial reason for locking up. Clearly, submission is the core aspect of chastity, and most men simply appreciate having their penis effectively removed from use, handing over control of release—and potentially orgasm—to another person. Men in relationships often report higher satisfaction because being locked helps them concentrate on their partner's needs and desires rather than their own urges.
Others do it as a method to manage behavior, such as curbing excessive masturbation, either with the help of a key holder or through various self-locking techniques. I suspect for many people, it is a mix of these factors.
Personally, I am self-locked and single without any specific compelling reason other than wanting to see where chastity leads me so far. My biggest hurdles have been mostly mechanical: finding a device that allows 24/7 wear without disrupting my daily life in the real world. I'm not sure about distinct benefits for myself personally, but I've enjoyed the experience and am eager to see how it unfolds.