What are the benefits of solitary practice?

I have heard about buddhist monks who undertake strictly solitary practice for 6 months where they practice entirely by themselves. They have no human contact and some of the other monks will come and bring them their food. The other monks will leave the food at the entrance and only when they leave the solitary monk will come out to take the food. I'm very interested in this way of practicing and would like to know what the benefits of such concentrated practice is and the fact that there is no human contact or contact with the outside world.