When you write book, whether the book is Novels, short fiction, poetry, personal memoirs, monographs, non-fiction, research reports, essays, newspaper, magazine, periodicals, research Journals, historical Archives, bibliographies, rare books, thesis, textbook, old archives or other written forms, we do so in order to get paid. It's incredibly rare that anyone writes a book with the sole plan of giving it away for free-even non-profits tend to think in terms of the purchases or donations they can get by offering a certain book.
But there are certain situations in which giving away a product for free makes sense. Sometimes it's only on a one-time basis. Sometimes it's giving away that book to everyone who wants one. When it makes sense to offer your product for free:
If you want people to write reviews of your book, you can't count on them purchasing a copy of their own. If you haven't built enough awareness of your book yet, offering a review copy for free to someone may be the only way to get that person to even look at what you're offering. You can afford to be selective with who you offer review copies to, though, so don't feel like you need to give a copy away to anyone who asks.
Giving something away for free can be a major attention-getter. If you're working to build an audience and demonstrate your expertise in a given topic, giving away a free book can be a fast way to do it. You do have to promote a giveaway almost as hard as a sale, but giving away files (essentially free to copy) can be inexpensive next to many other kinds of marketing.
Sometimes we do something that isn't about the money, like donating your book to a group that needs it to truly make an impact. Giving copies of an book about building a better career, for instance, to a non-profit that specializes in working with the unemployed can be a situation where there isn't a financial upside but that makes you feel personally rewarded.
There can be direct financial rewards for giving a product away for free if you do it right. Giving away a copy of a great book to every person who buys a high-priced product.
There are plenty of other ways to give away your product for free and come out ahead. Of course, you do need to eventually make some sales, but these situations can help you create opportunities to sell your products.