I think a big difference is that an unused Google Drive it has no impact on you, so most people don’t have a good reason to want to close it. Whereas people open and close social media accounts all the time (for personal and social reasons alike).
Also, afaik you can create Threads profiles without Instagram, so conceptually they are separare from the start. You are effectively penalizing Instagram users.
I think you can deactivate your Threads profile, at which point it wouldn’t really have an impact on you (I’m not sure, I don’t actually use Threads or Instagram). And they’re very clearly branding Threads as “an Instagram app”, so the fact that it uses an Instagram account isn’t too surprising. Having two separate accounts could work too, but at the moment it doesn’t really seem unexpected or detrimental that they’re the same account.
