I don't know about you but I have a mental program that I go through before, during and after each shot. After the shot I do certain things depending on whether I'm shooting targets or critters. One of those things is to return the turret to zero before I do anything that has to do with changing from the task at hand. I'd guess it's just as easy to forget and use the wrong hash mark for "hold overs" as it is to return to zero. I can guarantee you that the first time it costs you dearly, you will remember to return to zero.;)
Even if you have the zero stop, it's not automatic. If you can remember to use the zero stop you can remember to return to zero.
Having said all of this, have I forgotten to return to zero? YES! Did it cost me big time? Yes! But, I still think it's just part of the mental game of long range shooting. It's just that sometimes my mental game goes a little south.
I heard a very well known smith on this forum say in an electronic format I happened to be watching, that he had once gotten so wrapped up in all of the pre shot preparation for a long range shot that he forgot to dial the turrets, got in behind the gun and took the shot. Needless to say he probably hit a "little low".