You are right that writing code glue code is a large part of software engineering, and that knowing what the libraries do is an important part of that. But once you know (or think you know) what the libraries do, how quickly do you bash out the code that does that? Do you struggle, or does it just come naturally?
And as faul_sname pointed out, often the quickest way to understand what the library does is to look at it. Is that something you’re capable of doing, or are you forced to hope the documentation addresses it?
Other times you want to write a quick test that the library does what you expect. Is that going to take you half an hour, or 2 minutes?
You are right that writing code glue code is a large part of software engineering, and that knowing what the libraries do is an important part of that. But once you know (or think you know) what the libraries do, how quickly do you bash out the code that does that? Do you struggle, or does it just come naturally?
And as faul_sname pointed out, often the quickest way to understand what the library does is to look at it. Is that something you’re capable of doing, or are you forced to hope the documentation addresses it?
Other times you want to write a quick test that the library does what you expect. Is that going to take you half an hour, or 2 minutes?