What AnnOMaly said...that the partaking and being anointed creates a separation (paraphrasing), i think that is right on.
Also, the decisions way back to eliminate Christmas, birthdays, etc. - seems to me frees up more money for contributing to the WT, was the main reason! The secondary reason was to create hatred of JW deliberately, isolating them more from normal society. (Which is one of the warning signs of an abuser, isolation.)