By giving freebies, you can increase sales in so many ways. As the customer who bought the original product, If you like the sample then you might buy the product. Or If you pass the sample to someone else and they like it, they will buy the products from the company.

For example if you write an ebook on a topic, give them the Table of Content, and one or two chapters as a sample. If they like the topics or like the way you write the topic, they will buy the ebook from you. By giving free sample, we are minimizing their risk. They don't have to worry spending money for something they don't like.