Again, this is one of those questions where one has to ask why the military does something and if it makes sense for civilian use. Just because it's mil-spec doesn't mean that it unilaterally the "best" ever.
The military has the option of full auto fire. FA fire is much more rigorous on the recoil buffer assembly. It's much more important in FA that the castle nut does not move and the buffer tube does not loosen if the rifle is to function correctly.
In contrast, **most** civilians will only fire semi auto, ever. Sure, bump stocks and triggers that intentionally cause doubling exist, so extended "fast semi auto fire" means a greater chance for the castle nut loosening. If that is how you roll, just stake it.
Soldiers have no choice in their buffer tube extension. Civilians can reconfigure their buffer tubes to rifle, carbine, or pistol tubes (with the appropriate buffer and spring). If you want to make it easy to change your configuration or don't want to have to purchase new end plates, then don't stake it.
Soldiers use their rifles for things other than actually shooting. If someone is going to stand on your rifle, if you need to use your rifle as a pry bar, or if you plan to use your buttstock as a striking tool, by all means, stake your castle nut.
If you go to the range, take your rifle out of the gun case, fire 50 to 500 rounds of semi auto fire, and go home. You probably don't need to stake it.
.....unless it's parkerized under the FSB - then you must stake it
.....or you have to change the buffer tube on a 6920 - then you must re-stake it
If you go to the range and need to tell everyone how tactically ready you are for the next zombie invasion, go ahead and stake it.
I find it hard to believe the "50 rounds to loosen" comments. I'm not saying it didn't happen. I'm just saying that the nut was probably not tightened to the spec torque to begin with.
Now the kicker. I want you to think about all the A2 rifles out there..... rifle length buffer tubes and fiberglass stocks..... buffer tubes held on by friction....
It's literally the pre-applied loctite on the stock screw and the stock indentation that keeps the buffer tube on. And even then, the stock usually wobbles. The only way for an A2 buffer tube to wobble off is if the tube wasn't tight to begin with. Then, you see the gap between the lower receiver and the buffer tube extension. Let it go long enough and the stock will turn right before the tube comes off. How often does that even happen? Very rarely.