The RTOS which exist today did not exist in the mid-1980s. Neither did off-the-self servo and stepper motor axis controllers. The PC was still 8-bit.
That is why real-time data acquisistion systems, machine control and avionics were developed in embedded real-time operating systems designed and developed from the ground up for 32-bit processors like the Z-8000, 68000, and NS-32000 series, usually on VME bus or Multibus.
By 1987, I was able to develop modular RTOS with a micro kernel and plug-and-play device drivers, for the Intel 80286, which is totally portable to the 80386 and Pentium chips. Once you have done that, why would you spend time and money using QNX, VRTX, Wind River - which are intended for programmers who don't know how and don't need to know how to create the OS, only the application. My RTOS has support for the PC console in all modes, as well as RS-232 terminals, a windowing system in text mode and a GUI, which most of those commercial systems lacked until recently, and still lack.
OS/2, being a genuine real-time operating systems which had a GUI interface, made a lot of sense for machine control, and was used for that. IBM mismanaged its development and application.
Over 98% of the software running in the word is embedded real-time, much of it still written from scratch, starting on the iron. Others have enough memory and board size to use 8, 16, and even 32-bit commercial operating systems. Many still use microcontrollers, like the ARM or PIC, with their own little RTOS tools.
