Going to the app-store allows for reading opinions (i.e. somewhat independent) compared to just clicking, go-on. It shows some download/usage statistics and the like.
Also removal of the app guarantees removal, removal of web-works, etc. is significantly more cumbersome. Personally, I have very little trust in browsers (with their constant updates, sort of rushed) and have set deletion of all cookies/storage/etc. on exit - hence convenience is not there.
Overall web browsers make for a poor man OS w/o any specific hardware support (unless you count virtualization to a degree) for privileged layer access.