I am running a Greyhawk game in OSE, and have taken to creating my own Random Encounter tables, where there are 2d6 results , but the results clustered around the bell curve are things like 'herd animal', 'random location', 'merchant caravan', and the monsters are towards the downslide of the curve. The VTT also gives me the ability to nestle charts within charts, so that 'herd animal' then goes to another 2d6 chart with different animals, and larger, rarer, or more dangerous ones end up along the edges. I can then do that fairly easily for different terrain, or add modifiers to either chart to generate more dangerous encounters were I inclined. Doesn't mean a Dragon might not appear in certain terrain, but less likely than using the standard.
I agree the charts were weird, and I prefer the extra work of creating the couple charts for a country like Sterich, rather than trying to do the whole of Oerth. I also like to curate the monsters appearing in the world, so the 'kitchen sink' of the MM and the random charts doesn't really help.
There's a quick sentence buried on the first page of DMG appendix C, under "
Procedure: when a random encounter is indicated by the periodic check, and you do not have an encounter table specially devised for the area, roll a d20." So yes, there's an implied assumption that a lot of the time you'll be designing your own local area encounter tables, but they don't really explain that. And then, of course, Appendix C goes on with page after page of elaborate tables which implicitly argue for their own use in their existence and great detail. Later books, like the campaign settings, and the back of MM2, in particular, talk much more about building your own encounter tables.
I have a question why significant long-distance trade through the frontier is expected?
Right, this is a larger context which most folks aren't clear on unless they read closely- are these wilderness encounter tables intended ONLY to be used in totally uncivilized areas? If so, how should the procedure differ in civilized areas?
OD&D seems to assume that the whole procedure is for use when exploring wild, uncivilized and unknown areas, though it muddies this by mentioning there being cities there.
Book III The Underworld and Wilderness Adventures, p14-15:
THE WILDERNESS: The so-called Wilderness really consists of unexplored land, cities and castles, not to mention the area immediately surrounding the castle (ruined or otherwise)which housed the dungeons. The referee must do several things in order to conduct wilderness adventure games. First, he must have a ground level map of his dungeons, a map of the terrain immediately surrounding this, and finally a map of the town or village closest to the dungeons (where adventurers will be most likely to base themselves). "Blackmoor" is a village of small size (a one-horse town), while "Grayhawk" is a large city. Both have maps with streets and buildings indicated, and players can have town adventures roaming around the bazaars, inns, taverns, shops, temples ,and so on. Venture into the Thieves' Quarter only at your own risk! The terrain beyond the immediate surroundings of the dungeon area should be unknown to all but the referee. Off-hand adventures in the wilderness are made on the OUTDOOR SURVIVAL playing board (explained below). Exploratory journeys, such as expeditions to find land suitable for a castle or in search of some legendary treasure are handled in an entirely different manner.
Book III The Underworld and Wilderness Adventures, p 16:
REFEREE'S MAP is a wilderness map unknown to the players. It should be for the territory around the dungeon location. When players venture into this area they should have a blank hexagon map, and as they move over each hex the referee will inform them as to what kind of terrain is in that hex. This form of exploring will eventually enable players to know the lay of the land in their immediate area and thus be able to select a site upon which to build their castles. (Castle building and its attendant requirements will be covered hereafter.) Exploratory adventures are likely to be the most exciting, and their incorporation into the campaign is most desirable. Exploration by foot is at normal speed. Horsed parties will travel at the speed of a draft horse, and exploration by air will be at half normal flying speed.
AD&D expands it to cover civilized areas, with different encounter tables. For example the one split between pages 186 and 187, Temperate And Sub-Tropical Conditions, Inhabited And/or Patrolled Areas- for which a bunch of monsters are possible, but 28-80 on the d100 chart are various forms of men, including a 28% chance of merchants and a 10% chance of pilgrims.
I took a peek in both my World of Greyhawk campaign setting books and my 1E Forgotten Realms campaign setting book, and both have local area encounter charts, and modified odds of encounters in civilized lands. In civilized plains areas, for example, FRCS suggests a 1 in 20 chance of an encounter on entering a given hex (two procedures are offered, though; that or the DMG one). FRCS also gives instructions to create shorter local area encounter charts.