I worked at multiple airline reservation shops in the late 80's and 90's, all of which used IBM's Transaction Processing Facility (TPF). There were C compilers

I worked at multiple airline reservation shops in the late 80's and 90's, all of which used IBM's Transaction Processing Facility (TPF). There were C compilers available towards the end of the 90's, but they were slow to be adopted, nominally because the hand-written assembly could be better optimized to meet processing time constraints. I think some of that might have been a bias on the part of the long-term programmers who had vast experience in assembly and did not care to learn C.