I know several not-authors that believe this, as well. Yet, anecdotal evidence from several patrons suggests they’ll spend more money on authors they’ve tried from a library and liked. And several buy the books they’ve already read. This was well before the plague years, but I bet it’s still true.

I went from never hearing of an author to buying signed copies of all her work direct from her because I read the novels at the library first.

Absolutely. Libraries are my "try before you buy" hack. Sometimes I find a wallbanger, but mostly it's $$$ for the author in addition to what they got paid by the library.

I have an entire section of shelving for Star Wars novels because I found Timothy Zahn and Michael A Stackpole at the library when I was a pre-teen. I eventually lost interest and haven't bought anything new in decades, but there are dozens of books I have from those alone.

I’ve bought books as gifts that I originally read at the library.

High key! I like to try one book from an author, or the first book of a series, from the library, and if I liked it I'll buy them going forward.

Right! As a kid, I'd read a book from an author, and if I liked it, I would go buy their books. (I sometimes buy the same book more than once, over the years.)