However, there is a workaround. You can redirect a Shop Page to a category page (to which you can add Shopping Worlds).
1. Create a Shop Page, for example 'About Us (placeholder)'. Make sure it is active, and then in 'Link address' add the URL of the category page you want it to redirect to.
Note: I'm not sure if it matters or not, but I've been adding '(placeholder)' to my Shop Page names so they're different from the corresponding category page.
2. Create a new category under your root category (usually English), for example 'About Us', make sure it is active, and tick "Do not display in top navigation".
3. Go to Configuration > Cache/performance > Cache/performance, open the Cache tab and clear all the caches.
Done! You should now see your category page instead of your Shop Page when you visit the url, for example `about-us/`.