It's definitely an important skill, but it's also an incredibly fundamental one. Professors don't have time to spend on this for the same reason they don't have time to spend teaching you how to study well, or what proper English grammar and punctuation is. They'll just give you a poor grade if you can't manage it, because those are skills you're expected to have a grasp on coming into post-secondary education.
And by "don't have time", I mean above and beyond what they already provide in sessions meant to provide support to students on precisely those subjects, and their office hours. Classroom time is limited, and needs to be focused on the actual content of the course in question, not basic reading skills. And yes, "how to read academic papers" is a "basic reading skill" at the undergrad level.