Touchscreen support. For example, I use Zinio to read magazines. The webapp can't zoom, doesn't handle portrait mode well, and is pretty bad with touch. Actually it's pretty broken in general. But the Android app runs great on my Chromebook and has a good fullscreen touch UI.
Similar with something like Google Play Books. The Android app has a good fullscreen touch UI and has a notes feature that the webapp doesn't.
Having offline apps is game changing because not everyone has access to the Internet all day long, and doing tasks like image and video editing on your laptop will be much easier and faster than using web services.
You can already side-load Android apps on ChromeOS, as well as with Chrome on other platforms. All you need is the ArcWelder chrome extension, which I'm pretty sure is provided by google themselves, to package up an apk into a chrome app: https://chrome.google.com/webstore/detail/arc-welder/emfinbm...
If it's get too affordable with a low-end hardware, most users will still opt for LAN cafe which is popular in China and some countries and is cheapest option for gaming and surfing Internet.
It's a pretty huge deal, at least in my eyes. Chromebooks have this enormous following because of the price. Now, every app in the Play Store is installable to this huge group of laptop users. That means when a company wants their app to be on Android, they consent to it being on laptops as well. This means Microsoft Office and Apple Music are on ChromeOS laptops. It's a very effective strategy to vastly increase the viability of Chromebooks for regular users using other companies' apps. I never expected to see Apple developing apps for a Google-controlled laptop OS, but here we are.
Similar with something like Google Play Books. The Android app has a good fullscreen touch UI and has a notes feature that the webapp doesn't.