Windows does have a built in dictation tool, you can even us it in .net (i am for my side project).

I've often wondered about this. There are any number of desktop environments for linux, but I haven't come across any that are speech oriented.

One reason I can think of is that there was no incentive to build speech recognition because in most organizations that use computers, people talking to their computers is likely to disturb everyone around. But with more and more jobs becoming work from home, this may not be such a problem in future.

I wouldn't be surprised to see it shipping with Chrome sometime in the near future.

Dictation is built into recent versions of OSX.

https://support.apple.com/en-us/HT202584