This is a complex issue with many contributing factors.
Not every student needs to learn how to learn at the level you are teaching. They may later, of course, and some students do well for a long time and then hit a wall when things get hard. Some struggling students go farther than some early superstars because they learn how to work at it and the superstars found it too easy and don't understand why they are now having problems.
Many faculty members, I think at the beginning of a career especially, don't realize that their students are not like themselves. They get doctorates because they can learn relatively easily in the environment in which they were taught - usually lecture and exam in many places. But their own students may not do well it that same environment (what ever it is) and so don't have any easy tools for teaching those students.
Furthermore every student is different in how they learn. And many students don't know when they have learned something and so make unfortunate assumptions. Some students read something and think they have learned it, when they have not. They have only a short term memory retention of what they read, not a true understanding.
Generally speaking we learn through reinforcement and feedback. Learning requires that we re-connect synapses in the brain, physically changing its structure. See The Art of Changing the Brain by James E Zull for a run-down on the science behind it.
What to do
I think that every faculty member has a responsibility to teach their students to learn as necessary. This means being always aware of what is happening in their course, getting sufficient feedback on student learning and making sufficient course adjustments so that anyone with the desire to learn can do so.
Sometimes the most effective way to teach a subject, say computer science, is to interrupt the course and spend some time teaching the students how to learn CS. If you can make them more effective learners then everything else will be much easier.
For example, students may not know the value of taking notes, nor of summarizing their own notes. They may not know the value of always carrying something from which they can study (book, notes, index cards, ...). It isn't hard or especially time consuming to teach people the value of such things. I ended class periods with a call for the (say) three most important ideas of the current lecture. I sometimes asked students for the most important idea of the previous lecture. It takes a couple of minutes to do this and sets the stage.
So, I think that the presumption made by the OP that this doesn't happen isn't necessarily true. But the need for it isn't universally recognized, when IMO it should be.
In fact, you can teach people to learn your subject if you just require them to do tasks that give the necessary reinforcement and you also give them the required feedback. Don't assume that they have learned anything because you have lectured on it. Give them some sort of exercise or project that will induce the necessary changes in the brain. Then give them some feedback on how they did. Even better if you can let them re-do assignments to correct misconceptions and give better and more positive reinforcement. This can be done instead of any formal teaching them how to learn and can be just as effective. Maybe more effective, actually, as it is more organic.
In particular, active learning methodologies results in learning as it requires the active participation (reinforcement) of the student. The student doesn't need to "learn" how to learn the subject matter. The course activities themselves provide for the required learning changes to the brain.
I'll note that the Pedagogical Patterns project has spent quite a lot of effort on the issue of teaching technical subjects (especially CS) to people who have different learning modalities. So, it isn't that the issue has been ignored.