Having done just enough robotics stuff to have used linux before (though not controlling anything even kind of large), I find this an odd notion. It's not that

Having done just enough robotics stuff to have used linux before (though not controlling anything even kind of large), I find this an odd notion. It's not that I think linux would go wrong for this sort of thing often, but when dealing with things like rockets or self-driving cars I'd think you want more assurance than "well we haven't had it be slow yet." I haven't messed with an RTOS before but have done some fooling around with scheduling on microcontrollers and I can see why linux is tempting for ease and speed. But we're talking rockets and self-driving cars. These things are expensive as hell, can easily kill people, or both. It seems like the exact sort of place you'd want to take the time and effort to be sure.