That's a bad-faith argument. The vehicle already had no spare... Using non-run flat tires, as you have suggested people should do, would put people in peril. The fact no spare is included is actually a great reason why you SHOULD STICK WITH run flats.
Reduced tread wear: A 2013 study by J.D. Power found that people replaced their run-flat tires an average of 6,000 miles sooner than owners using conventional tires. Opinions differ on the reason, but one theory is that tiremakers put a soft tread compound on a run-flat tire to counter the hard ride. A side effect of the softer compound is a shorter tread life.
JD Power is a joke in the industry. No one cares about their findings, outside of paying to win their "awards" which are used for marketing purposes.
Your mileage may vary (ha ha ha, get it?) but my experience has been that run flats last as long as any other tire. My wife got 46k miles on her tires and she could probably go a little further... But we're replacing them proactively. On my vehicle, which does not have run flats, I only expect to get around 35k miles on my tires... Different vehicles, different tires, different expected life. A quick browse of TireRack shows reputable Run Flat options that include tire warranties, and those warranties are comparable to the non-run-flat options in the same size/load/speed ratings from the same brands. So I think the claim of less tire life is dubious, at best. But for sake of argument, let's assume it was true, for a moment: I'd gladly accept a 6k mile shorter tire life in exchange for the peace of mind to know my wife will be safe in the event of a puncture. She doesn't have to stop in a bad neighborhood, or at night, or in bad weather. She can simply drive home. Worth every penny!
Blowouts are still possible
No shit. Do you not care about eating healthy or exercising because you
could still die from a heart attack? There is still immense value from the
significant reduction in likelihood of a catastrophic failure. The overwhelming majority of the time, run flat tires reduce the severity of a failure and allow the driver to continue driving at a reasonable speed for a decent distance (my wife's tires state 50 miles @ 55 mph).
Hard to tell if it is low on air
Your premise is so unlikely as to make your statement basically a lie. No manufacturer uses run flat tires on a vehicle without a TPMS system -- so you will easily know if the air is too low. Even if your vehicle didn't come with run flats, from the factory, all manufacturers have been mandated (in USA) to include TPMS systems since 2007.
Again, bad faith argument. As you have admitted, manufacturers tune the ride quality to meet their targets.
This is the first (and only) thing you've said that has an ounce of truth. Run flats do have a slight price premium. It's about $30-40 per tire, in my experience. Whether that is "worth it" to you is a personal choice, and I don't fault anyone for deciding "yes" or "no" to that question, for themselves.
Less on-shelf availability
That has not been my experience. When I was shopping around I found several shops that had my run flats in-stock. The bigger issue was installation availability. Even shops that had the tires didn't have time and were booked at least a week out. I ended up ordering on TireRack.com and the tires were delivered to my home the very next day. They're sitting in my garage until my appointment, on Wednesday. Availability is certainly not an issue.