Mint has the shield in the bottom right bar -- A little red exclamation point appears inside the shield when it needs to update. It's a reminder to anyone with any semblance of sense that an update is available. It's not too unlike how when you're speeding down the motorway and your oil light comes on. People notice the oil light but somehow seem to miss the little red exclamation point in the shield.
I'm going to put the blame squarely on Microsoft for this whole not being mindful of updates thing. For literally years, quite nearly an entire generation even, here's Microsoft running it's processes in the background on a box being used by a totally oblivious end user. No mention of updates at all until all of a sudden .... boom ... the screen goes dark because the system is rebooting due to an update (Win 98, ME, 2k, and XP were notorious for this). I don't have a clue as to how many hours worth of rewrites I've had to do because Microsoft didn't give any notice about a potential upcoming reboot. (Windows 7 did give some indication of a reboot toward the end however) This was one of the main reasons why I left Microsoft Windows in the first place.
Auto updates are the bees knees for most who don't want to bother with updates. One of the biggest selling points in getting my wife to use a Linux box was to let her in on the fact that it wouldn't just willy-nilly reboot out of the blue until she actually initiated the reboot herself.
The only time Linux Mint needs to reboot is if there is an update to the kernel itself, otherwise, you can update to your hearts content without so much as a passing glance.
I don't understand why they wouldn't upgrade, especially as users could leave themselves open to bad actors.
People that are still running a Linux Mint 17.x box are probably still using it because the newer builds have left their old integrated board graphics behind, and they either don't have the money for a newer (old) box or a graphics card or both.
I've got a few boxes around here that won't run Mint 19 or 20 without first installing a graphics card.
Speaking to the upgrade.
I've upgraded 2 boxes lately. From Mint 19 to Mint 20.
Though Mint is fast and light, and fairly easy to administer, I'll have to admit that doing an upgrade can be somewhat of a chore. I ran both upgrades through the terminal, and in the time it took to do that, I could have easily had more time for tea if I would have just backed everything up and done an install with the new build in the first place.
(manually upgrading through the terminal from build 19 to build 20 of Mint was still much faster than upgrading from Windows 8.1 to Windows 10 automatically, so at least there's that bit)
Upgrading is indeed a drawback, but even in spite of that drawback, I'll still roll with the Mint builds as they are released. (Mint is the only DEB build that doesn't look like Ubuntu - Ubuntu is fine, but it's rather ugly and I prefer the regular Windows type/style of layout)
I think that if Mint could reconcile the actual upgrades between builds, in an automatic way, without sacrificing speed and over all functionality of the system during the upgrade, we would have a winner.
As far as all of the other little updates that come along during the lifetime of the build version itself, I could go with auto or not, because that's not really an issue with me.