First of all, it’s cost-effective. If you want to make a theme by hiring someone then you have to hire a Designer and a WordPress developer which is so costly. Here you will get a premium WordPress theme by $59.
You don’t need to put effort into design & coding. If your content is ready then you just need to install the theme & required plug-ins and then import dummy content by a single click. After that, you can put your content and your site will be ready.