Why wouldn't a 2-tank-a-day-diver not want to know deco status? The DM might be busy rescueing some other suicidal diver, I want to know what's going on in my dive. Get the computer.
Do you believe that if they don't have a computer they have no way to know their 'deco' status?
IMO the fact that they need a depth gauge and a bottom timer anyway, a computer can be had for no less money. At that point they now have an ascent rate monitor at no or little additional cost.
IMV the average O/W diver (especially the newb's) should have an ascent monitor. I put it like this. Sending a new/inexperienced O/W diver to the surface without an ascent rate monitor is about the same thing as throwing a brand new/inexperienced driver out on the road, telling them to drive 30 mph and then covering up their speedometer. Can it be done, surely. Should it be done? that's your call. Is there a better way for those noob's... IMV yes.