And there are alternatives. But the core libraries are a safer bet for long term maintainability, and they get invested into to survive long term. A big thing

And there are alternatives. But the core libraries are a safer bet for long term maintainability, and they get invested into to survive long term. A big thing that people often don't understand about .NET is it has the perspective of being all things to all people. One example of this is that it gives first class support for supporting living extensible systems for long durations like decades which is often not really the case for other stacks. Hence the prevalence for approved long term supported libraries typically with first party backing from MS. Another aspect of this all things to all people is that it has lower level closer to the metal performance features that people only used to high level stacks often mention they don't see the need for (although they don't say it like that!). Another aspect is you can do pretty much any kind of application in it, from web to native to high performance games or latency sensitive systems (with some special techniques) to well almost anything. The ability to access low level performance while still having high level general ergonomic APIs is critical to this.