I think what most people don't get is that an app is a gateway to get way more personal data of the user than the browser. I'm distrustful of any "app only" service for this reason. I think the article goes into more detail about other good reasons. What you're suggesting isn't a talking point because it's not pertinent.

This isn't about a user's age, or mobiles. You can use Firefox on your smartphone. It's about digital literacy in terms of security and privacy. No matter how old you are, you do have to be taught that you're the product of these services, not just the customer. You have to be taught why that matters and how to combat it.