The author goes on to list what he sees as the advantages and disadvantages of random encounters, but quite remarkably to my mind never actually mentions the real purposes of random encounters in terms of setting and game design. So he lists Pros as being things like killing off annoying characters or filling time, and the Cons as serving no story purpose or throwing the wealth per level guidelines out of whack (and I need to rant about that some day). No mention at all is made of anything relating to the setting, or verisimilitude, or even resource management.
The post seems to ignore the two most important features of random encounters: naturalism, and husbanding resources. They’re the GM’s chief tool in presenting the setting as a world that actually contains stuff that isn’t there for the sole purpose of being part of the PCs story, and they are the game system’s primary reason the players can’t completely optimize their resources (particularly daily powers in D&D)–the chance of such an encounter is why players have to keep something in reserve.
(I’d like to get a bit of definition out of the way: by random encounters I mean any encounter that isn’t determined by story needs or the PCs’ direct actions. It doesn’t necessarily literally have to have come about by rolling dice on a table, though that’s certainly an option, but it’s something that isn’t required as a plot-point of the story or because the PCs have decided to seek out, say, the chief of the palace guard and have an encounter with him.)
Naturalism is important, in my opinion, even if you’re running a story-oriented sort of game. If the setting contains no features at all that aren’t independent of the needs of the story, then the world will lack all verisimilitude and feel flat and lifeless…if it doesn’t degenerate into parody. The central joke of Knights of the Dinner Table, after all, is that the GM is stuck with three players out of four who refuse to see the world as containing any features that aren’t clues, prizes, antagonists or (rarely) allies. If there’s a cow, it must be a magic cow and they capture it and drag it along; if there’s a gazebo it’s a hostile encounter. But if you don’t have random encounters, then the players will be absolutely right in assuming that if the GM bothers to mention it, it must be significant. The world will lack any depth. This, btw, is the curse of many of the graphically intensive computer RPGs…players correctly assume that if something can be interacted with on-screen it must be significant, because the programming and art resources won’t be wasted on mere flavor. But if the setting contains random encounters, and the players are aware of it, they are thrust in the much more realistic position of no longer knowing whether something they run into is there by chance or design. They have to reason about the logic within the gameworld instead of logic about the story, which I think is not only much more satisfying, but makes for better stories. If the players can correctly reason that the vizier is secretly the bad-guy, because viziers are always the bad-guys and besides, he has a goatee, the resulting story only works as a comedy.
While naturalism is valuable for pretty much any kind of system, resource management is peculiar to certain kinds of systems and settings…but is a particularly important part of D&D and its progeny. If you have a system where resources are defined in terms of their availability per day, per encounter, etc, and are replenished by rest (rather than, say, going back to the store and buying more ammo) then it’s an essential part of the design that the players have to consider whether they’re likely to have to call on those resources at times not of their own choosing. The random encounter is what balances the X times a day abilities against those that can be used continuously (such as swinging a sword). If you take it away, either you have to add time pressure to every scenario (which can be quite a strain on verisimilitude) or you have to ramp everything up (or scale the resources back) to match the assumption that the party will always have its full resources and be willing to expend them all.
You could think that it needn’t truly be random, and that as GM you can just devise the encounters just so to make the party expend resources at precisely the right pace, but IMO you’d be wrong. You’d be wrong because the players aren’t stupid, and they know the game, and they know that as GM you have infinite resources to throw against them, so they will reason that if you hit them with something when they’re particularly low on resources it’s because you’ve chosen to be unfair. Which is true. Without randomness whatever you do to them you’ve explicitly chosen to do. But that means unless you’re willing to be a jerk and kill them just because you can (and good luck getting people to play with you once you’ve established that reputation), you had better not hit them with anything challenging when they’re low on resources–unless you’re also willing to cheat like mad so they come out on top despite it. But if they know you won’t do that then they’ll be all the more likely to spend all the resources they’ve got and then turtle.
Openly and publicly using random encounters is the solution to that whole set of problems. If they know that there’s a certain chance of random encounters per period depending on the environs, and some of them might be hostile, then it’s up to them to decide whether to hold something in reserve or chance it–and whether hunkering down in place to recover resources is worth the risk or even possible. The GM doesn’t have to decide to punish or not punish them for recklessness or over-caution…the setting has certain known features and the players can roleplay whether and how much risk they want to take given the stakes and circumstances.
If you’re really considering whether you will eliminate random encounters in your game, what you really need to think about is how you intend to convey the texture of the setting and not give sense that the PCs are locked in The Matrix where everything is just an illusion for their benefit, and in a D&D-like game how you’re going to deal with the players wanting to blow all their resources in each encounter and then to sit around and recover them for the next encounter. Random Encounters aren’t the only way to deal with either, but I think they’re one of the simplest and best approaches I’ve seen.