Why is separation of OT and IT Networks recommended?

Operational Technology operates differently than IT, and fulfills very different needs. Add to that the fact that most IT experts are not trained in Operational Technology, and those who understand OT are typically not IT experts. The different roles of the technology combined with the knowledge gap between these 2 groups makes running one converged network challenging.  There are also safety concerns of putting security systems on the IT network which may make it more accessible to hackers.