Why do many web developers hate jQuery?

I think jQuery is a much needed library, but I don't understand why so many developers hate it and try to replicate the same functionalities with plain JavaScript.

For example, take a look at this repo. It claims we don't need jQuery and explains how to replicate each jQuery feature in plain JavaScript. Well, what's the point? jQuery exists to make your life easier - why reinvent the wheel?

What do you think?