Uhh, more like: "If you see one of them, you can be damn sure the next two are right around the corner". Because every single time you meet an elemental monkey in Gen V, you meet all three. Either one trainer with all three, or consecutive trainers with one each. They never appear in isolation, maybe except for the Battle Subway.
Also, you meet the elemental monkeys all the time. It's like the designers tried to cram them into every route in the games. They had their own Gym. They came in their own giveaway. They were in Big Stadium and Small Court. Morimoto had all three. As do lots of other random trainers. They are easily among my least favourite Pokémon, because of how much they were shoved in our faces (and how much they outright sucked).
What I meant by "looking around for a while" was "being able to
catch all three (in Pinwheel Forest)". Not that you'd
want to, seeing as you've already got your Starter covering one of F/W/G (and the gift monkey covering another) but it's cool how rare they are.
Admittedly, they are pretty popular among Trainers, but I think this was the developers' way of reminding players about type matchups. Looking at it this way, the monkeys show new players what types do, compared to many other games where there weren't many F/W/G Pokémon at all apart from your rival's starter (see D/P). As you see them later in the game, you start learning new things about their types: Pansage resists Sandile's Mud-Slap, Panpour can be taken down by a Spark from Blitzle, etc., and they prepare you for said rival battles by teaching you like this. I'm sure many a new player has learned that after fighting that Panpour, they figured out that they could beat Cheren's Dewott with that same Blitzle. When you finally meet Morimoto in the GF building, it's a "final test" of sorts, and due to his team's high levels, it's harder to get around the monkeys by strength alone. You have to remember to use that Zebstrika from way back when, hold back on using Krookodile against Simisage, and so on.
Tl;dr The monkeys are actually quite an ingenious way to teach new players about type matchups. We experienced players might not like them as much due to their repetitive designs, not to mention that we already know about type matchups, but for new players, they can be a big help (especially considering the fact that you have to deal with two rivals in BW).
Defending these monkeys has made me like them more for some reason. I wonder why?
Edit: Although it isn't quite my .25K yet, I'd still like to thank everyone in the Orange Islands for teaching me to write long, informative, and above all fun to read posts. I won't tag anyone quite yet, though, because 250 isn't that big of a number (but it's a start!).
