I'm only speaking for myself, not other authors. As with most authors who write books on technology, I don't depend on my income from writing, so it might be different for professional authors whose primary income is from writing.

But personally, when I went to a local library, saw that they had two copies of my first book, and both were checked out, I was incredibly proud. I love libraries. I guess overall, I would make more money if everybody who checked out my book at the library bought it instead, but I don't care.

Libraries buy ebooks with your property tax dollars. The more patrons read, the more copies they buy. Authors and publishers like this.