First, I think that this question needs to be moved to the Discussion section of eNotes. I believe that you will receive many different answers there.
In Harper Lee's novel To Kill a Mockingbird, Boo Radley, essentially, hides from society. The reason/s behind why Boo hides are objective. What this means is that each reader makes a decision as to why they believe Boo hides from society. Harper Lee does not provide the ultimate reason as to why Boo hides--it is left to readers to speculate. Therefore, any explanations regarding Boo's hiding from society are speculative. As with any justification, one simply needs to provide evidence to support their stand.
That being said, I believe that Boo hides from society based upon the fact that he is aware of what society says about him. He, most likely, has heard the rumors about his character and actions. Unfortunately, instead of facing society, he is either forced by his father or makes the decision to remove himself from society all together. The important idea lies in the fact that Boo chose to enter society at exactly the right time--to save Jem and Scout. From this point on, Boo's reputation should change.