@ SMS and Taxi.
sundaymorningstaple wrote: I've never used a dive computer but plan my dive and dove my plan using the old fashioned, but non-breakable method. Again, Sorry. Your sixth sense is picking up somebody's vibs, just not mine.

Yes, that approach would be entirely appropriate if you know you have to go down say the leg of a rig, boat hull or pier to fix something at xM, i.e. a fixed point.
But recreational diving is usually (as I know you know, but I'm elaborating for those who might not) 'Multi-level'. So you start you dive, go down to maybe 18 Metres, and then slowly tootle along a reef wall looking at stuff, come up to 14M and continue, and finally up to say 10M, where after maybe 40 minutes in total you decide to end your dive, ascend for a 5M/3m safety stop, and surface.
Now when you do your dive certification (IME), you have to calculate your gas 'Pressure Group' through a dive like that. It can be quite complicated. Or put it another way, the opportunity to get it wrong is probably larger than is desirable.
I imagine that's why PADI introduced an electronic RDP some years ago (it's like a pocket calculator). It's a little less daunting than being handed one of the plastic/'slate' RDPs for the first time.
I think that's the beauty of computers. It allows you flexibility, you no longer have to 'Plan the dive, and dive the plan', you can change the plan whilst on the dive.
It used to be that the average American worker got 2 weeks holiday a year. So maybe a dive enthusiast might spend a week off on a diving trip. Take out the day of travel, and the 24hr 'No Fly' window at the end, and you can see why there is a market for getting the max out of each dive/day/trip!
Or how about if you're diving on gas-blends, where perhaps you're on Nitrox 32%, and your buddy has a fill that tests at 35%. Unless you compromised and both dived as if on a 32% mix, you can't share 'No Decompression Limit' (NDL) information.
It's funny, when I've been on dives where people are on EANX, it seems to go hand in hand that they wish and try to completely max out their NDL. I imagine paying the say US$10 premium for a Nitrox fill does that (lord knows what it would be like amongst a bunch of kiasu local divers lol

). As an aside, when I dive on Nitrox, when I get back on the boat, and we're sitting on the boat waiting for dive #2, I'll quite often (when not talking) chug away on what's left of a nitrox fill... the DMs tend to ask what on earth you're doing, but accelerating the off-gassing seems to make sense to me.
The thing with computers these days is how multi-functional they are. They also serve as a wristwatch, a compass, and alarm clock etc. So if you're relying on that also, and it instantly dies on day #1, it is a bit of a pain! For example: I had to adapt to waking up, and judging the time based upon the number of mopeds going up and down the little road behind the place I stayed. Not exactly ideal or relaxing when you have to get up, get ready and have brekko for say an 8am roster
p.s. Taxi. Would you be kind enough to PM me the name of your dive-shop contact? I've just remembered today that I need the 'balance arm' in the 1st/Secondary stage adjusting of my Mares regs fine-tuning. Unfortunately it has a small leak and needs a minor tweak. Ideally I need a shop-owner who is knowledgeable enough to do this adjustment himself, without having to send it off to Mares. Time is running out and I need to find some options as to how I might get it fixed [You will probably know what it's like after years having your own kit, having to use a hired set of regs... not nice, and actually a damned distraction!)