The reason some manufacturers don't put one there standard is because the gaskets are soft and will 'squish' when tightened. After a few heat cycles they get smaller and go hard, so the nuts have less tension on them, then they unwind. It's kind of funny that the nuts still come loose on a lot of them though. I'd put it on there, and put some Anchor Locks or something similar on the nuts, haven't seen any problems so far.