Sure, it can waste paper, but I often find it convenient to print off blog posts or web sites for later reading. Partly because it’s just impossible to read anything of length on a computer screen.
But very few blogs have a print facility. And even those web sites which do, such as most newspapers, are usually not convenient. For example they may not enable one to do a print pre-view. Or the print format may be horrible. Printing straight from the browser usually produces a cluttered result with often unreadable font sizes.
Imagine printing this page directly: