I think it's pretty safe to say that the majority of us are here to avoid another corporate takeover of our preferred platforms. It would seem to me to be a tad irresponsible to allow Facebook into our space with open arms, allowing them to hoover up our data. I would love to keep using Lemmy.world, but will happily change instances if need be, and I feel many share that sentiment.
There is no real need right now. Lemmy is focused on following communities, not individuals. This is more of an issue for Mastodon than Lemmy.
It might never be an issue for Lemmy. Threads would need to start organizing people around communities, or Lemmy would need to encourage people to follow individuals (something Reddit promoted and no one cared about)
They weighed in months ago back when it was announced and said they were taking a wait and see approach, where if it did cause problems they would defederate, but didn’t want to preemptively do so. Many other instances did defederate already though.