Just the simple trick of zooming in on a website with a "2 finger pinch/pull" is something a big part of the population doesn't even know how to do. I know my mom would probably just give up.
Buttons on many websites are way too small for some people to use.
Those are never an issue on native apps. The UI on apps scale with the size of a phone's screen. No matter if you have the smallest iPhone or the largest Android.
This alone is enough for many people to not use the web browser unless absolutely necessary.
Most of the people writing on HN were first exposed to the internet through web browsers. On the other hand, children these days who grow up with smartphones first interact with the internet through phone apps. Do they have any difficulty adapting to the unfiltered web when they grow older?