In most areas of chemistry, standard units are adopted - we never would think to use ounces (even American chemists resist) BUT even in modern journals or textbooks, we commonly still see the unit
mmHg used. Why is this the case and why have people not moved to adopt SI units in this situation?
To give an example, consider the "Purification of Laboratory Chemicals" book that is often referenced here. Many distillations are given using pressures in mmHg.