HN Why are there no real time hardware/operating systems available?

There are? QNX and VxWorks (Integrity maybe, depending on your definition of "OS"). If you want the hardest of hard real-time, you'd need to use a CPU that doesn't even have a cache... =;-}

They are used in very specific applications, from industrial robots to cars to mars rovers. They aren't better in general, just suited for the specific use case