This write-up articulates the issues from the perspective of a security lecturer. The core issue really is ownership of technology.
https://techrights.org/o/2021/11/29/teaching-cybersecurity/
Whatever the appearance of competition between, say, Apple and Facebook, Big-Tech companies collude to maintain interlocking systems of controls that enforce each others shared values including sabotage of interoperability, security and inviting regulation upon themselves to better keep down smaller competitors. Big-Tech comes with its own value system that it imposes on our culture.
I question whether a lot of people even need sync.
Passwords in general don’t change for long periods of time. Really the only rationale for doing so is confirmed or suspected compromise (two-factor processes make this rarer still). It doesn’t strike me that an almost permanently static input merits regular synchronization.
The alternative is doing a one-off manual sync (copy and paste) between two local DBs, then locally moving one of them to the target device. Zero online connectivity has to dramatically reduce attack surface. Is five minutes’ maintenance per year an unacceptable convenience penalty to pay?