Its my belief, that the reason they dont use them is because the stock touches the barrel the entire way down, affecting accuracy. Secondly, the old M1 Garand and mausers had full length stocks partly so you didnt burn your hand on the barrell when you grabbed the end of it to shove the bayonette into a mans lung.
the m16's and such that have bayonette lugs still use handguards on the end of their barrels.
Yeah spade...good luck holding the barrel of a weapon that has just fired how many rounds in battle?
I saw a sporterized M1 on the net not too long ago and it was horrific lol. Obviously lots of time and money went into it, but with the sights removed, hunting sights added, and a monte carlo stock it was stomach turning to see lol
As spade says, most modern battle rifles still have nearly full length guards on them. For sniper rifles, we do not need the utility that the full length guard provides, we need accuracy, which comes from floating the barrel, which pretty much is a pain in the neck if you have a full length hand guard/forend.