If you all feel comfortable not staking a castle nut, great. To suggest it's the way to do things is unresponsible & ill informed. The mechanical engineers that put the recess in the caste nut, to allow metal from the staking process to push into the castle nut, ensuring it would not back out knew what they were doing.
This forum, tends to have a more proffessional/informed perspective than the usual
www.anecdotal.crap
I have seen FACTORY assembled: HK, Colt, BM receiver extension tubes all come loose. If not for the staking the reciever extension tube would have backed off allowing the buffer detent to pop up rendering the weapon unusable. You can still fight with a wobbly stock, not a seperated one.
Cause: Poor assembly process. A castle nut should be torqued, backed off & retorqued 3x like a barrel nut & then properly staked in two positions. Tolerance stack will determine how tight the reciever extension tube (buffer tube improperly said) will fit in the lower reciever.