Although I have grown increasingly frustrated with the Kindle ecosystem, I don't think this is a fair complaint. Amazon lets you download a sample of any book in their library, which is usually pretty substantial -- can be multiple chapters depending on the length of the book.
I use this mechanism as my "shopping cart" where I just freely download samples of books that seem even slightly interesting. Later I can browse through my backlog, start reading, and either file it away for later, buy it, or delete it if it's clear that it's not for me.
Everyone's different. You find that a sample that Amazon chooses for you is sufficient for you. OP finds that physically picking up the book and looking at whatever they want is sufficient for them.
The OP specifically mentioned using z-lib to get electronic copies of the books.
I agree that physically picking up the book is a satisfying experience; I find myself often browsing in physical bookstores or libraries in order to find material that I will buy on my kindle. But that's not what OP was saying or that I was responding to.
I use this mechanism as my "shopping cart" where I just freely download samples of books that seem even slightly interesting. Later I can browse through my backlog, start reading, and either file it away for later, buy it, or delete it if it's clear that it's not for me.