You've already been hammered with the privacy benefits and yada yada.
So I'd like to outline another major benefit: being able to authenticate to the same service with two different set of credentials. (i.e. logging into the hosting provider with both my personal account and the company's)

At the time of writing this is not working with Sync and there is a lengthy discussion on Github about the challenges of that.
Why it would certainly be nice to synchronize it's still useful as it is.