I think I wasn't clear enough. You are absolutely correct in your assessment of those guys, 30+yrs of live system is a big deal. Its the guys these days who, despite the tech having moved forward, and problems having been found, and solutions to those problems being well tested, still insist that modbus is the way to go in new systems, "just run it over ip, it'll be fine, we can artificially limit concurrency out" (their method is DoSable in at least 4 ways).

Sometimes "its been done this way for 30 years" doesn't mean "nothing better has been found", it means "there is a lot of inertia and stubborn-ness".