Better question is why don’t both use a dot like URLs do because people have had 30 years of getting used to that:

username.lemmy.world

Plus this wouldn’t get confused with an email address.

Don’t worry, your successor isn’t offering anything big. You’ll still be around for many more days to come.

^ How to make sure your app has no users.

The reason design has become homogenised is because we want things to be intuitive so that users don’t have to learn. They just know. And a more useable app beats a less useable one. Always.