H2Andy:(read on at your own risk; this is just my opinion)
it may not be the diver's fault, but it's ALWAYS the diver's responsiblity
to get back on the boat. it's my job as a diver to get back on the boat,
not the operators'.
Not always. Maybe in areas where the boat will anchor yes but in other places where conditions arent as benign - windy, swell, current, tides and so on its normal practice for the boat to never anchor and divers are picked up by the boat coming to their marker buoy.
Its the divers responsibility to have and deploy a suitable marker boy BUT that also relies on the skill of the boat crew of being in a position to see it and come to you. For a variety of reasons this isnt always the case.
Sometimes the boat is waiting for you when you surface, sometimes the boat takes 5-10 mins to get to you if he's picking up/dropping off other dives, occasionally 15-20 mins if someone else has a problem. Generally more than 30 mins you can assume he hasnt seen you so should be looking. After an hour if he hasnt found me then id trigger a PLB.