Most new books I find are books I check out from my local library. While the library did pay for a copy, so it’s not quite the same, as a reader I didn’t pay anything for it. The barrier to trying the new book is very small, and if I don’t like it I haven’t lost anything.
Readers finding your book online for free are having the same experience. Maybe not everyone who reads it will want to buy copies, but some will. Just like how some who find your book in a library would want to buy their own copy.