It’s all about Linkability
This is not just whether your great site, with perfect content or tools and your pretty layout will make people want to link to you. It’s also about making it easy for them to (deep)link to you, and to exactly the content they are interested in. Don’t make the mistake of thinking you made it easier for people to use your site when you let them stay on one page. People have been browsing the web for quite a while now, and they expect to go from one page to another when they click on a link. It’s not that they’ll leave if that doesn’t happen, but you’re denying them the possibility to deeplink. In that process, you’re denying yourself a whole lot of deeplinks. And thus a whole lot of Google love.