That reason is they want to fly CSAR and NSW; not VERTREP.
TERF & Low Level through the mountains has been the most fun I've ever had in the aircraft, especially Day Terfs in the PI!! (No rules there)
CSAR and NSW are exciting missions, hence movies and books on the topic. I'm still waiting for the Hollywood movie on VERTREP...
Says the F/H guy who probably advocates straight in approaches for VERTREP.
Let it be known that the Phrog was the best VERTREP aircraft to ever fly the pattern, but I have known many HSC (60S) pilots who have continued the tradition of stick skills + good crew coordination to get the job done. VERTREP, when done correctly, has been some of the most rewarding and challenging flying I've ever done in a helo.