Because the real world is not as neatly compartmentalised as you would like it to be, and these are high school kids, not grad students?
If you're teaching high school auto shop, does their class need to include the social and economic impact of the automobile? Hint: The answer is no. It's a course on a specific subject. It's supposed to be compartmentalized.
They can and will hear all about social issues in all the classes that don't actually prepare them for real jobs. No, they're not grad students, but they're old enough to complete a course that focuses purely on the technical. Previous generations somehow managed it.