When you invest work into a code-base that depends on something like .NET, you are taking up some stake in the community and ownership of that base. You do need at the very least security updates, but you also need support and documentation. It's hard to describe fully in words. And most of the time, you can't just switch that particular part of your stack overnight. I'd rather be stuck with a community that looks healthy.

And you can argue about the trade-offs of different "ownership structures", and compare for example the .NET foundation over the Django/Python foundation over whatever Java is currently doing.