They seem to prefer it this way.
Strong doubt. What's lower friction, "visit this address in your browser and login to start configuring" vs. "go download this app, open it, possibly log in and register an account, add 'your' device, and only then start to configure it"?
Let's also not forget the possible chicken-and-egg situation of needing the Internet to download an app to setup your new router to access the Internet...
You're obviously one of those computer people.
Cloud command and control is obviously a better user experience, and it is much more secure.
I’d never defend the lack of web based configuration, but there is an argument to be made that if the app uses Bluetooth to communicate with a router (though I don’t know if that’s true in this case), it is inarguably easier to configure for the average person who is intimidated by having to work with an IP address in any way.