I think that wilderness is only useful to specific adventures and can be replaced in many other kinds of games.
Speaking of wilderness I mostly speak about untouched by civilization vegetation wilderness (forests, jungles, hills, grasslands, swamps) and not extreme biomes such as deserts and rock mountains.
My first postulate is that the smallest 'unit of setting', for the lack of the better word, is almost always a made structure – a dungeon, a city, a ruin, a building, a landmark. Even if in a forest there is an altar of root-god, made from roots and carcasses of animals without a human hand ever touching it or there is a hollow tree where fey lives, both are still _structures_, something that is made to have a certain (human or not) function, something where interesting things happen.
Barring all of these kinds of places, the wilderness itself is amorphous and featureless, or, rather, having most of its features blended. On the map it is mostly a place that is defined by its borders and by points of interest (which are almost always a structure such as a settlement, ruins or some kind of landmark) within those borders.
Pointcrawl is a type of play that especially navigates the wilderness between points of interest, which are usually structures.
Why the wilderness exists, when we speak about the setting of the game?
• It exists that the setting is believable, because IRL wilderness carries a very important function to supply life to the planet, and changing this drastically will immediately make the setting looks more artificial or SF (as in Blame! or Numenera)
• It exists as 'blank history paper' for more history to happen when borders of civilization has to be expanded (royalist rebels run into forest, merge with beasts, fight back, eventually overthrow the regime and create a empire of Beastbloods with the seat in the forest which is also now their citadel).
Setting history-wise it can be as simple as 'the Kingdom of Yrith built its mighty fleet from golden trees of Old Forest'
• It is the place where enigmas and horrors can be hidden, to pull out (sometimes as deus ex machina) some unpredictable things, such as beastblood union above, without much complexity. If setting needs a mystic coming with never-seen-before-revelations, strange beasts or buried secrets, the wilderness is one of the common place to 'store' them until they appear to be known by the rest of the works.
• To simulate complex RL wilderness mostly through random encounters.
• To simulate the long dangerous travel and use of resources (food, time, wounds, nerves).
• As a 'quiet time' filler area between more intense parts of the game such as dungeondelving.
In computer games and RL it is also to give you strange vistas to immerse into setting more and know its deep beauty, but in tabletops it mostly loses this function because few people are willing to listen to long descriptive paragraphs, therefore such descriptions should be done well (both evocative and succinct) to work.
There is another layer to it: the players' upbringing and 'skill'.
By my personal observation the vast, vast majority of DnD players are of urban upbringing. Some from smaller settlements, some from huge cities, but few are immersed into actual wilderness to the point of being as intimately familiar with it as the rest is with the cities. When I see a forest I can tell very little about 'how it works' aside of what I read in books and from very rare travels through it; I mostly see such forest from urban perspective anyway, in terms of difficult terrains and paths. I don't know what most of the forest means, how different layers of it interconnect. When I am in urban area, I can say what is below my feet, where unseen streets go and what each sound is; I see a ruined building, I can have a pretty good guess what it was and what befell it just by looking at it. Even in an unfamiliar and confusing city I am not near as helpless as in the forest. Players learn urban environment by osmosis and at the end, I believe, they know a sort of language, to understand this environment and its features with much greater details than the wilderness where features has no much distinction. Their characters might know the wilderness but then it is mostly a roll of the die, not an actual interaction.
As a result of such familiarity players instinctively have more 'tools' to interact with urban-like environments. From my (limited) experiments, the same random encounter monster in a wilderness almost never provoked people to use environment to the degree they used when in urban decay areas. Trees were to climb up and hide behind; the urban decay was to crush unstable walls onto a monster, to electrocute it with leftover cables, to lure it to chemical vats, to block yourself in small rooms. Most interesting was that the number of questions 'Is there [X] around [for me to use]?' noticeably grew when players dealt with urban decay environment in contrast to the forest.
This is noticeable in old-school dungeons where players look for traps not by the roll of the die but by player skill and asking questions.
I wonder – if aesthetics are not important and if a setting tone permits, won't it be more interesting to replace the wilderness with urban decay and over-structures-overgrowth to give players an environment with which they can interact more?