Ask Lemmy

There are multiple reasons depending on who you ask and the specific instance:

• Privacy - Meta has a really bad track record of user privacy. There is the worry that federating with them will result in them scraping user data from users (which IMO is a bit silly - Meta can and probably is scraping all the available public information anyway, defederating doesn't really fix that).
• Moderation - Meta is notoriously bad (compared to Fediverse servers) at moderating their content. Admins and mods don't want to have to spend a lot of time dealing with trolls coming from Threads.
• Terms of service - I've not looked into it, but I assume that Threads have a strict acceptable use policy on content on other instances, which presumably they enforce unilaterally. Instance admins might not want to deal with complying with that, so just don't bother federating at all.
• Ideology - "The fediverse should not be influenced by a company!" Not all instances are like this, but there are some that see the fediverse as a statement against capitalist greed and megacorps.

Not trying to shame ya or anything, just educate. This was a very easy thing to find using the lemmy search function, here's the top result when searching "meta threads".

Edit: I share site functionality and link a very thorough discussion that is relevant to the question and still get downvotes. Awesome, yall have a great day.

they are afraid that they wont be able to stop themselves from utilizing any of Threads bells and whistles thereby making themselves dependant, or that they are incapable of moderating sub-scripted content flowing from Threads.

most just hate meta so very very much as to not want to associate with them.