It's extremely important to know what words pair with each other. In the past, not many people knew about the idea of collocation. Teachers and textbooks did’t usually provide information about it. Words were almost always presented by themselves. In recent years, language teachers have started to pay more attention to collocation, but you'll still find a lot of books and courses that don't address it at all.
Learners who aren't aware of collocation won’t bother to learn what words go well with each other. Most English learners think of learning languages in terms of vocabulary (individual words) and grammar (a small set of sentence patterns). Collocation falls somewhere in the middle