I have Microsoft Visual Studio Community 2019 Version 16.8.4 (it's free)
and it supports C11 and C17.

While an upgrade for Community is free, for Pro/Enterprise without an annual license it's not. They've gone 100% subscription now, but people who have outright purchased in the past would now have to make that decision. The other problem is that a large version update can consume a large portion of a day, or even a week if it all goes horribly wrong, especially if your real job is supposed to be building things with it. Then you get to deal with the fun time that is deprecations and new warnings (and potentially new bugs) hitting your other codebases. If you're in a team, it'll have to be a team consensus and effort, since you probably need to be in lockstep. If you're restricted by corporate policy to software that's gone through specific approval processes, that takes even longer. All of this contributes to weighing all the cool new stuff you get against all the irritating everyone who uses it, thus the inertia.

In some ways it's a lot easier being a home user who can experiment with the bleeding edge and use whatever they want with their projects, but we don't pay the bills like the big companies with big governance do.

-Em