The act of shunning is so high school. What really does it prove!
I believe in past years it was a discipline that was supposed to "awaken" or shock the "sinner" into changing their path and "repent".
More recently, I believe it is a tool of their "information control". I suspect if apostasy and doubt have not overtaken immorality as the #1 reason to be DF'd then it is damn close. Plus many who are DF'd for breaking the JW moral code will seek out "association" and stumble across apostate websites (like this one) where they usually soon learn TTATT. WT cannot have the R&F who are too lazy or too dumb or too apathetic to question and reason on things to get into discussions with those who have already done so.