You can do the same with cp too. Also safer.

But I use Ventoy nowadays.

I didn't even know Lemmy existed until last week (when I specifically searched for a Reddit alternative) even though I heard about Mastodon.

And it might be confusing to decide where you need to register and what's the difference without reading up how the Fediverse works. Most people don't care about that.

Also if they are based on the same technology why I can't use a Mastodon account to login/interact with Lemmy (conveniently)

I guess if we ever have Nomadic identities most of the above could be solved? Except that Lemmy is still almost completely unknown for most of the people.