Are these really necessary? I have a Noveske rail and installed it without the pin because my receiver doesn't have the hole, and I'm not sure that its worth the money to have it done professionally, not to mention weakening the upper slightly by drilling another hole above the gas tube hole.

It seems to me that 6 bolts into the barrel nut will do just fine in keeping the rail from rotating. I don't think an aluminum rail is an effective lever to loosen a steel nut anyway, or am I wrong? I'm just curious if these serve any real function beyond just existing to assure the whatifs that their rail wont rotate.

The Hodge rails also use this feature (carry over from the Mega Wedgelock design, it seems) I can see that barrel nut/rail design needing such a feature since the rail is held on by friction and could theoretically rotate on the nut if enough force were applied.