I'll play Devils Advocate here. Having done the Spiegel Grove multiple times and being a non-deco recreational diver my experience differs from your description in many ways.
1- I don't drive all that distance and wait all year just to dive the SG. I plan a dive trip that will be perhaps 12-18 dives over 5-7 days. I do other things during the trip such as dining out and sightseeing and just plain relaxing so it's not "all about the diving" although it's "mostly about the diving".
2- My dives on the SG average about 40-45 minutes because most of what is to be seen on that wreck is in the 60-80' range. In my opinion 40 minutes might as well be 20 minutes. The dive has to be longer than the drive. I'd rather climb a ladder once per day than three times per day. Being aware of depths and maximizing bottom times by staying a bit shallower on average can make quite the difference. 2 - 45 minute dives on the wreck are more than enough for me. I was a boat captain in Key Largo, most tourists aren't actually doing 40 minutes. On a recent dive we swam from the stern mooring, through the wreck almost to the bow and back again. Yes, on one dive we saw most of the wreck. Not possible when you're checking out every deck.
3- It can also get somewhat chilly when you're in the water close to an hour or more. I don't mind the SI to relax and warm up and enjoy some time in the sun. I've never been chilly in 80 degree water, even during 4 hour dives.
4- I have no interest in hanging on a line for an hour looking at nothing but an occasional passing jellyfish. I bore easily. I sleep and an hour is NOTHING.
5- Totally not worth the expense and extra gear and the weight of the additional tank. Besides where does a technical diver on vacation rent a rebreather or double tank rig anyway? Technical destinations have doubles to rent. Rebreathers are such that they can fly with you.
6- So my bottom time is about 1.5 hours vs your 3 hours. It's not clear to me if you are including deco stops in that 3 hours, if so it's a no brainer that it's not worth the extra trouble to tech dive under those conditions. Even if the deco stops are over and above the 3 hours it's still not worth it. That's a ton of time in the water. Some people would rather be in the water than surrounded by people seasick on the surface. Also are the other non deco divers sitting there waiting for you to decompress after the second dive when everyone wants to head back to the dock? If you're the first person in the water, and the last person out of the water, people aren't waiting for anyone. It takes roughly an hour to get everyone in and out of the water. There's another hour for SI, then another hour to get everyone in and out of the water. 3 hours. I've done this enough that my dive profile/plan balances with the last person on the mooring line waiting for the ladder. Add in the fact that technical divers typically gear up and stow gear than the other divers, and no one really waits on us.
