it's amazing how we never learn. Things that Perl and CPAN and Linux distros figured out decades ago are constant issues today. It wasn't that long ago that NPM didn't even have checksums. CPAN runs unit tests on install. I can't imagine how slow that would be with npm.
Package signing is, well... I suppose that's another lesson from the '90s people will learn about soon enough. With a web of trust as broad as python or npm you'll just have everyone running around with signing keys and "trusting" any key they come across because none of it is built on personal relationships. When Archlinux asks me to confirm adding package keys, what am I going to do? Say no? I don't know these people, but I want my shit to work.
When it comes to my personal laptop, I also, typically, blindly trust the keys coming from developers because I don't have time for that. Not so much if I have to deploy a system into environment that several orders of magnitude more expensive than my laptop...
With systems like Python, I'd imagine that a solution to web of trust would be that some group of developers would organize a curated set of packages. So, for the cases where you need better security assurances, you'd use that. I mean, of course there's no guaranteed solution for the web of trust, but, in practical terms, something like that would be good enough for regulators.
There's already stuff like NumFOCUS. They don't particularly focus on the technical side of things, or endorsing more secure practices, but, in principle, they could. Maybe there will also be others once we have been bitten more times by some security breaches.
Package signing is, well... I suppose that's another lesson from the '90s people will learn about soon enough. With a web of trust as broad as python or npm you'll just have everyone running around with signing keys and "trusting" any key they come across because none of it is built on personal relationships. When Archlinux asks me to confirm adding package keys, what am I going to do? Say no? I don't know these people, but I want my shit to work.