It is for both but rehabilitation and punishment. But in this case I do agree but let us say he had panicked shot and killed someone during that robbery.

Even though he would have lived his life the same most people would probably feel uneasy about a completely suspended prison sentence even if the man and his actions afterwards might have been exactly the same and that he would be no smaller risk to society after going to prison, possibly the opposite.

But we (or I at least) would not feel it was not fair unless he was punished by prison.