Less reliance on a single instance means, the single instance is less likely to fuck over their members (via advertising or data sharing)
Less likely of a situation where one instance can create a sort of monopoly of Lemmy communities and take them private via defederation, leading everyone to join that singular Lemmy instance to see the content.
I think I meant more so like does it matter because we can still all see the same content regardless where we sign up right? From my basic understanding of this fediverse or whatever the hell it's called lol