Okay, followup question -- when was the last time anyone saw the key change and actually did freak out?
If you're using VMs, keys change all the time. Maybe some people here are good about security and would freak out, but I'm thinking about workplaces I've been at, and that's not a typical attitude for developers that I know. If I set up a VM at work and changed the keys on it, I doubt my coworkers would even ask me about it when they saw the warning.
And I'm literally right there -- they're not going to file a Github issue for a developer they've never met asking why the key changed and then stop working until they get a response.
To push the point even more, how many people on here actually wrote down the SSH fingerprint that they got the first time they connected to a remote machine? When you got a new laptop, did you transfer the keys over, or did you just blindly reconnect to every VM again?
Package managers are meant to help you manage installs on multiple machine, so it's not just the first time you use a package -- it's every time you do a fresh clone the repository, it's every time you throw away your cache and do a new reinstall over the network.
And it's based on this idea that even when doing an update, package managers and developers won't just blindly hit OK if they get a notification that a key changed, which I just don't think is the norm, even in technical circles.