Other people probably have different behaviors. People I know with younger children in particular use local libraries for children's books quite a lot.
But libraries as a place you checkout books is almost certainly already on the decline. For me, the pirate sites aren't even competition. I only have limited time. I read a lot on the Internet. If there's some new book I want to read, I'll probably just buy it for my Kindle. (Obviously many people are much more price-sensitive but I wonder how many of them are using libraries today.)
I suppose it depends on your library’s offering and how many books you go through
Other eBook readers from firms such as Kobo or Onyx start at about $100 to $200, and again may be found used for a small fraction of that price.
That's still a hurdle, but roughly the cost of a new trade-paper volume with the capability to hold many hundreds or thousands of books.
Depending on what you're looking for, there are ebooks which can be found, legally, free of charge from sources such as Project Gutenberg, Standard Ebooks, the Internet Archive (both to check out or to download with no limitations), and other libraries. The US Library of Congress has been expanding its own offerings (I'm not up on the latest, though am given to understand it's generous), and many large-city libraries (Boston, New York, Chicago, San Francisco, Kansas City, etc.) have extensive digital lending programmes.
That's without leaning on book liberation sites such as ZLib, LibGen, or Anna's Archive, though those have quite extensive holdings.
I've always been surprised that they haven't cracked down on it, given the relative ease with which you can circumvent the necessity of the Kindle store for the majority of popular titles. Simply load up Calibre, pop almost any file type into your library, and away you go. We're really living in the Limewire age for e-book piracy, even if we don't realize it.
My guess is, someone has run the math and figured out that it's better to keep people on a Kindle device and occasionally spending a few dollars, in exchange for the slow death of physical media and legitimate alternatives. When those become less readily available, then perhaps you can begin to boil the frog.
You can be sure I won't buy a kindle if I can't sideload onto it. I buy at least 5/6 new hardcover books a year from local independent retailers to support authors I like. I wish more authors would allow an e-book copy to be distributed with hardcovers they sell. Do what vinyl did.
My county library system has about 100k ebook titles and another 30k audiobooks. I've probably read or listened to well over a hundred library books since the last time I actually went to the library.
ADDED: Indeed. They use the rebranded Overdrive (Libby). Last time I looked at (maybe) Overdrive ages ago it seemed to be highly populated with things like self-help books. Looks useful.