no unified password management (or even worse: everything gets just attached to your google/ios account - i hate apps that do not give me the option to keep stuff separate)
no history functions (esp. over multiple devices)
single apps getting bought out by marketing corpos or bad actors without getting notified
data sniffing apps are harder to reign in than my sandboxed browser tabs.
NO ADBLOCKING AVAILABLE IN APPS
I'm sure there are a lot more reasons, that's just what came into my mind