All the above points are valid, however Rotorspeed flight into IMC with no warning does happen. I've seen it in the UK on 3 occasions. One minute VFR, the next fog all around and me sitting in a shrinking hole in the middle of it. The other area no-one has mentioned is the instrument failure situation. A while ago flying an IFR approach into a major airport at night I experienced a screen failure which took out my HSI but left the picture in place. I was very confused for a while just as I was intercepting the localiser. Fortunately I squeaked for help from the ground and the approach controller effectively gave me an SRA until I was happy with my scan taking in the LH seat instruments. I was working hard and I dread to think what would have happened had it been a flight director failure or multiple failures and I was left with the standbys.
My eternal thanks and respect go to that controller at EGGW!