Keeping the congregation clean
And apparently a pure calendar
...all create an illusion of righteousness, which is the sole purpose of the WT from a theological perspective IMO. Since real righteousness is an impossibility for humans, the best they can do is to simply imagine themselves better than their peers through such devices as considered on this thread. The WT is the pimp that feeds this drug to the addicted.
When understood this way all the nuttiness makes sense.