This thought has also crossed my mind.  The mosaic law was a tutor leading to Christ, Jesus fulfilled the mosaic law - end of. Â
Why do we keep quoting from the OT?  The WTBS seem to draw on the OT more than any other, using it out of context to pass sweeping judgements on a whole gender - as we saw recently with the WT article on women.  Why keep dwelling on rules and regulations that no longer apply, especially in this, the 21st century?
Simple: The Watchtower doesn't teach the New Covenant. They know nothing of the freedom of Christ, and their legalistic approach is better suited to quoting the Law, that is no longer in effect.
Usually their articles say something like:
"True, we are no longer under the Mosiac Law, however.... (fill in some rule they want you to follow)."