I'm in an area that requires conduit. I've always used plastic insulating bushings on all threaded fittings (inside of boxes). Over the past few weeks I have noticed that both of my big box stores have stopped carrying them.

I paniced a little, then decided to dig through the 2005 NEC. I do not see that they are required.

Are these things really required? Do I really need them?

Halex P/N 75205B is a sample in case you do not know what I am referring to.