There's an (unverified) myth that retention on mobile apps is better. This is one of those things that marketing people keep telling each other without ever verifying the facts. (Unless you deliberately make the web version inferior, of course.) The reasoning behind it is that you should take real estate on the user's home screen at all costs, because your app's icon will serve as a reminder and people will allegedly…
I think there are provable cases where an app almost certainly leads to less retention than more and something like Reddit, whose value lies in allowing you to explore the internet is almost certainly one of them.