Partly sim training, where there is an engine failure on every approach and every overshoot. Biggest problem becomes understanding the autopilot system and keeping the speed above Vy -tall order for most pilots. Engaging IAS becomes the solution of choice for instructors trying to get their students to pass a checkride in a couple of hours of training.
In the real world nobody flies IFR at the speeds that I see pilots or SOP call for in training. Normal ILS is flown at 140/150, with the occasional slowing down to 90 inside the FAF if the weather is crap.
Pilots in sims always want to fly it a Vy - guaranteed banishment to Siberia by a controller if you try that in real life. Slow flying means not much margin for error before you get on the backside of the power curve, or below IFR coupled airspeed, stupendous wind drift correction, etc. Again by pilots that never fly to minimums except in a sim on a checkride.
I like ALT PRE engaged to a VS or vertical profile a-la-139 style, and ALT to hold an altitude (or Rad Alt offshore). Throw in the IAS if four axis but generally who cares as long as you are fast enough to stay ahead of the Airbus a mile behind you that seems to never have a problem getting in at 150 knots with an eye reference point 50' above yours.
I've actually seen the argument in this thread carried to the point of some pilots not coupling to a vertical mode at all in cruise, and maintaining altitude with a fixed collective and hat trim! On a four axis helicopter.