The incentives on the web are skewed, and I believe the same is true for print. Nobody will be happy to pay the same price for a 50 page book as they would for a 200 page book, even if the information is the same, so if you have a 50 page book, you have every reason in the world to add fluff and stretch it to 200 pages.

For many articles on the web I believe it's an issue because of Google. Google does punish short pieces, so if you want to write about how to do X with Y, you need to start of with a history of Y, lay out a couple of use cases of X and then explain why doing X with Y is difficult, to finally explain how to do it.