Good point. Well, your numbers are a little off.
My car as 110,000 miles on it. I've raced my car a good bit (legal track racing, of course).
The first clutch (stock) I destroyed was by adding a 150hp NOS system on.
The second clutch (performance) was destroyed by my ex-wife driving it uphill and she slipped the clutch the whole way (like 5 miles). She obviously wasn't very good with a stick.
The third clutch (performance) was actually from old age.
My friend has a comparable car. It's the same engine, transmission, body style and weight. She drives more normally than I do (no racing, just city/highway driving). She had her clutch changed at 100k miles. Labor to replace the clutch is about $350 to $500. Parts are about $150. This car happens to be a bastard to work on, which is why the labor is high. So, $500 to $650 for the job.
This is about the age that an automatic transmission would need to be rebuilt. For this car equipped with an automatic, removal, rebuild, and replace costs about $3,500.
So, with my car, I've improved the efficiency by helping the airflow out (one minor exhaust fix, and a some intake fixing). I enjoy cruising at highway speeds with low RPM's (6 speed). The same car with an automatic would be cruising at a much higher RPM (4 speed), and suffering from losses related to the automatic transmission.
I rarely need to check my transmission fluid (i.e., gear oil). If my gear oil runs low, it could increase wear. A car with an automatic has to have their transmission filter and fluid changed. If their fluid runs low, it can be catastrophic.
There's about a 300 pound difference between the manual 6 speed and the automatic 4 speed.
So, lighter, better fuel economy, and less repair costs. I really don't see why people wouldn't want to drive a stick. The excuse "I don't know how" isn't a valid excuse, except they're too lazy to learn.
I can drive pretty much anything with wheels, and I've proven it. I'm licensed for motorcycles and cars. I've also driven everything including a big truck with a 10 speed air shifter. a neighbor bought a motorcycle, but didn't really know how to drive it. They told me it wasn't driving right, so I grabbed my helmet from the garage (I don't have a bike right now, but I still have the helmet), and took it for a spin. It worked fine. It was operator failure.
While I agree with much of what you have said, I call shenanigans on your assertion that 100k is about when an auto would need a rebuild. Other than in horribly abused vehicles, an automatic should last longer than that without needing service. While I hate car-related anecdotal evidence, I've personally driven two Ford AOD derivatives well over 100k without so much as a hiccup. The first, with an actual AOD, never had a transmission fluid change. The second, with the ever so unreliable AX4S, hit 155k before it was passed on to another driver. It still has not required a rebuilt several years later.