Hrm… I’ve thought about this before and failed to come up with any satisfactory answer. This isn’t a problem specific to Pokémon, of course – almost any combat-centred RPG has to introduce progressively more difficult opponents in order to keep the game interesting, and while most players are willing to suspend disbelief for something so clearly necessary to the functioning of the game, it’s still nice to have an explanation. However, this is easier for some games to produce than others, simply depending on the nature of the story being told and the world in which it takes place, and Pokémon definitely has more to justify than most.
I think the most obvious possibility is that you encounter more powerful Pokémon later in the game because stronger Pokémon become willing to challenge you as you get stronger (so we imagine that the strange level distributions are actually an illusion of sorts) but that doesn’t explain why you still find weak Pokémon when you go back to earlier areas. The weird thing is, NPCs in the games actually do acknowledge this pattern sometimes – for instance, if you try to head east from Santalune City towards Snowbelle City right at the beginning of the game, you’re stopped near the entrance to Victory Road and told that you aren’t ready for the kind of opponents you’ll find that way. It seems, at least at times, like the inhabitants of this world are well aware that some parts of their regions are much more dangerous than others for no readily obvious reason. I think what this has to suggest is that the skewed level distributions we see are very real, and that they can deal with it. Pokémon are not, in any real sense, in conflict with humanity as a group, so I doubt that towns in even the most high-level areas are in constant or unmanageable danger – you’d want to be careful walking around outside town without protection, obviously, but we’ve always received the same warnings about even the most benevolent areas at the beginning of each game. As for new trainers, it seems likely to me that a trainer’s career can start in a number of ways, and that in places with tougher wild Pokémon it’s more common to practice with and then inherit a fairly powerful starter a little later in life rather than be given a low-level one right off the bat (think about it – the trainer classes that represent prepubescent children like Youngsters, Lasses and Bug Catchers tend to hang out in the earlier areas of the game; trainers in higher-levelled areas tend to be older as well as stronger). Basically, their surroundings do present difficulties for Pokémon training as a career and an institution, but they manage to get around it. None of this, unfortunately, explains why some areas have higher-level Pokémon in the first place…
Pokémaniacal 