The modern dive computers are so reliable and so sophisticated that those can not be replaced by ANY kind of mechanical watch. Period.
A technical diver who is not using the most sophisticated modern systems for his diving is soon a dead diver.
Nicholas said it nicely: he wants to live with his watches. Same with me and because I am nowadays diving some 100 days a year, as an concervative person and a watch lover I am always wearing a mechanical watch as a backup.
I do not mean that I would ever use the alarm of Polaris for decompression stops, not even safety stops. But I will use the alarm to remind me about the end of the dive. Naturally, I could also use the computer.
In 55 minutes I will be picked up for a longish diving day with three dives. I love the feeling when I am ready in all respects except I have not decided yet if I will take Rolex Submariner, Sea Dweller Deep Sea, Fifty Fathoms of perhaps G-P Sea Hawk II with me for todaqys dives..
Regards,