Perhaps some of the problems are logistical. I know from experience that KLM, Schreiner, now CHC plus Bristow send two crew at a time and use their own instructors for conversions and checks. Smaller operators may not be able to send two pilots or have approval to use their own instructors thus making multi crew training difficult.
The rest of the world may be different to Europe for 30 odd years ago when I added the Puma 330J to my Indonesian licence there was no such thing as two crew concept,it was read the book, on the job training (helirig), written exam and soon as the papers were back captain on type.
On returning to the UK and put on the S61 it was ground school, training in the aircraft, written exams, line training etc. Starting to drift so back to sleep!