"Just recompile with the new version!" I hear the cries already, said by people that have never had to support literally a thousand applications in a government data centre, half of which were built years ago by a vendor that is long since bankrupt.
If you have thousand apps, you probably also have a CI/CD system and you can gain fine grained control on your runtime management needs with .net build/publish.
MS does quite a few things poorly but they have done a solid job of operating in large enterprises.
Or more realistically, dozens of CI/CD systems, covering less than a third of the applications.
The problem is if developers are publishing self-contained apps with .NET Core, IT staff will be up a creek on vulnerability mitigation. While being able to pin specific .NET Core versions is nice for developers, being able to require the most current .NET Core version be used is important for IT staff who have to support these applications.