If they did it on purpose! Unfortunately a lot of publishers are simply not educated on the eBook culture, which like the web page culture tends to prefer to set a lot of the formatting themselves. With eBooks we like to set the margins, fonts, line spacing, etc. to best suit our eyes. The old book printing publishers were used to having to make all those decisions for us and they are VERY slowly moving into our new eBook culture. It is very frustrating.

You can learn how to liberate and modify your books, just read around and use Google. But that is a PITA to have to do. Fortunately it is not necessary on most eBooks anymore.