It starts with a very basic, straight-forward technique. Let's say for example that uke is on his back and you're baring down on him. A relatively new or unskilled grappler will almost always try to push you off, to "bench press" your weight, right?
When he does that, he's presenting you with a straight arm. Naturally, you secure it and step right into juju gatame, end of story.
Consequently, most students learn or are taught very quickly, "Don't straighten your arms." Which now means you're rarely presented with the opportunity to use that juji gatame entry anymore. Which is great, right, because when your uke upgrades, you're forced to upgrade, and you both make each other better.
But then you realize no one's teaching that original, basic juju gatame entry anymore.
Or let's take the guard position. There's lots of fun things to do to your uke when you get him in your guard and he doesn't know to stay "south" of your belt and keep his posture upright: chokes, arm bars, turnovers, etc.
Consequently, most students learn or are taught very quickly, "When someone gets you in their guard, immediately posture up." Which means you're rarely presented with the opportunity to use all those fun techniques that require uke to be forward and "north" of your belt anymore.
But then you realize no one's teaching those original, basic arm bars and chokes from the guard anymore.
To be honest, I've skipped over teaching these sorts of "easy answers" myself. But I've started to ask myself the question, Why not?
Granted, straightening the arms or bending forward north of the belt is a rookie mistake, but hey, no matter how many students your school or any other has, the world is still chock full of rookies. And whether you meet them on the mat or "on the street," you're still going to run across people who make those kinds of mistakes.
I also can't help but think that you have to learn and practice the basic, "easy" entry in order to help understand what juju gatame (for instance) is and how it works. After all, just because your uke upgrades and doesn't straighten his arm for you anymore, doesn't mean you'll never use juju gatame again. You'll just upgrade your methods of finding or even creating it.
Sometimes I suspect we—in whatever learning endeavor, whether it be judo, aikido or piano or painting or surgery, or whatever—tend to eschew the simplest answers once we get to even an intermediate level. Perhaps we assume we're "too advanced" for it.
But really, how did we get advanced in the first place?
By practicing the basics, by mastering the simplest answers.