The history that we end up studying is almost always, in the end, history that we are personally interested in. If you imagine that you are going to spend several years studying a very narrow topic for your thesis not having at least some initial interest is going to make it even more of a slog that it already will be.

As for what we present there is a basic bias that no historian can escape. While we don't necessarily present only things that are interesting we do only present those things that we find important and relevant, leaving out many things we find irrelevant. Another historian may consider the things we found irrelevant to be highly relevant. It's the most basic historical bias that even the best historian can't escape because if you wanted to include every piece of information about a given topic your manuscript would become volumes in length. When I was in graduate school one of the articles on the required reading list for Historical Methods was an article about this basic bias written by, I believe, Howard Zinn.