Agree on the thread's in today's piping, as any burrs or slivers in the threads will cause leaks and a combo of tape and sealant will fill these gaps.
Short story about pipe taping I will never forget as a Service Tech installing etching and acid cleaning machines for electronics in the early 80's and a machine using 92% Hydrofluoric acid was leaking from the piping fittings. (this acid will eat through skin to the bone if contacted).
Dressed up in a hazard suit gloves etc., took apart the piping, and found that someone at the factory had wrapped the Teflon tape backwards (counter clockwise) causing it to bunch up and split the fittings and leak - could have been much worse - people getting sprayed and all sorts of liability - glad it was an easy fix.
So always wrap pipe tape clockwise.