It's probably not a surprise to you, but this is a hotly debated topic inside Canonical. And I apologize for that thread, as it really doesn't represent our best attempt at external debate.
Changing a paradigm usually involves pushing the envelope and breaking some existing assumptions; systemd is everybody's favorite example of that in the Linux world. The root of this issue with snaps is the trade-off between built-in security and user control. Some points to consider:
1. Browsers like FF and Chromium [on Windows] simply self-update, and disabling that requires configuration. So there is at least some precedent for taking the position that user applications should just update themselves. Server apps are more complex and are a strong argument counter to the existing behavior, as is the fact that many apps cannot be refreshed without user impact.
2. Ubuntu, since 16.04 LTS, ships with unattended-upgrades enabled, which means that for debian packages the default behavior is already auto-updating (although automated reboots are not enabled by default, as that would be crazy for the general purpose case). That feels like the correct default, too, given the risk of running code exposed to exploitable, public CVEs — and how reluctant users (like my dad and my wife!) are to click on "Install now" in the update-manager dialog.
3. Debian package updates run as root. Snap updates run in userspace, and confined. So in principle the risk exposure for snap updates is much smaller. And snaps do have an auto-rollback mechanism for failed updates [a]. Counter to that argument is the fact that snaps are meant to be under third-party control, and that there is no clear mechanism to separate security patches vs updates which you get with the debian pocket mechanism (i.e. focal-security vs focal-updates).
The lack of any official [b] means of user control over the snap auto-update mechanism feels wrong to many of us, including me. And while we may seem somewhat opaque in these debates, the feedback we get in threads like this one (and the snapcraft.io one) actually feeds into our decision making. So please do keep pushing on this topic and we'll do our part internally.
[a] See https://kyrofa.com/posts/snap-updates-automatic-rollbacks for a detailed guide on this topic. Of course, if your snap refreshes and you hate the new version, downgrading isn't quite always possible.
[b] There are ways to, hmmm, control auto-updating (i.e. refresh.metered, refresh.hold) if you really want to; that thread has a few. That doesn't help the debate, but I'm sharing in case someone has a technical need for it.