You may see that, Django has two different ideas in its structure. One is project and the other is app. Project holds apps. You can create as many as apps you need. But the question is how many app will you need? Just one or more?
For example, you are gonna make a blog. Now you can create an app as main which will manage the blog’s posts. Now your blog needs commenting. Let’s make another app. This app will control your app. Let’s add more feature like newsletter. Why should we not make another app for it?
Actually you should divide all major features into apps. If your blog will be small then you can do it in an app. But if you build a large blog, then you should more apps.