TLDR: a beginner can read, understand, and use the itertools module incredibly easily. But putting a recipe aside for your own use later? Forget it. That took my almost 3 years to get comfortable with.

Longer versinon:

I had this exact reaction for a very long time to doing this kind of thing (copying code and pasting it somewhere).

The main reason is, as a beginner, the entire concept of having a "bag of my own tools" in my own code somewhere (whether copied and pasted or not, doesn't matter) was very intimidating. And it was a near certainly I would forget that I put a thing somewhere to use later, anyway, and I knew it.

And if by some miracle I DID remember, figuring out how to package it up and import it later and fix it if it was broken (assuming that I wrote the code well enough to read and understand it 1 year later!) and then update the stored version and have it perpetuate into other code and tracking what I did and OH MY GOD BEGINNER BRAIN AHSPLODE. I think many people quickly lose track of how hard it is to be new to all of this stuff.