Take, for example, the "Losing Direction" Table on p. 46 of LL. As you can see, this table uses percentile dice to determine the chance of a party getting lost in the wilderness, by terrain type:
These d% ranges very closely approximate the "x in 6" chances listed on the analagous "Getting Lost" table in Cook's Expert rulebook on p. X56:
15% = 0.9 in 6 = approx. 1 in 6 (Plains)
32% = 1.92 in 6 = approx. 2 in 6 (Mountains, Hills, Woods, Ocean)
and obviously, 50% = 3 in 6 (Swamp, Jungle, Desert)
This discovery made me curious, and so I consulted a couple other sources: OD&D's The Underworld & Wilderness Adventures and Gygax's Dungeon Master's Guide. [The Swords and Wizardry Core Rules are excluded from my sample because they have no "Getting Lost" rules at all.] Guess what? With one exception (that wacky DMG), these rules sets (Cook included) all deploy the same d6-based mechanic for getting lost.
And while Raggi's Lotfp WFRP rules employ a slightly different mechanic, based upon the "Bushcraft" skill of the PCs (see Grindhouse Edition Rules and Magic p. 34), that skill system of his nevertheless uses the same "x in 6" mechanic that seems to be the prevailing choice for D&D authors.
As I just noted, the AD&D DMG is a notable outlier, for it uses an "x in 10" mechanic for lost parties -- here is the relevant part of its "Becoming Lost" Table from p. 49:
Obviously, this table disrupts the consistency of my sample, but hey, it is AD&D after all.
So, DMG aside, Proctor's Labyrinth Lord is the only classic D&D iteration I've looked at that uses a d% system for Getting Lost, and may also be the only one using percentile dice for dungeon stocking (I know Moldvay/Cook use d6's). I'm not complaining here -- for while I do generally prefer "x in 6" systems for in-game use, I have actually been enjoying using LL's d%-based dungeon stocking tables lately -- but I do wonder what made Dan Proctor go this route when basically no one else does?
Perhaps I should truck on over to the Goblinoid Games Forums and ask about this directly. But I wanted to get my thoughts out in a coherent way here first, and to see if anybody else in the blogosphere can shed light on this matter for me.