I say to each their own too. I very strongly believe everyone has a right to screw up their life however they want. But. It's not like these things you listed cancel each other out. If you have a few beers and get in an accident where you slide on your face for 20 feet, would you rather be wearing a full face helmet or no helmet? Safety is cumulative: well maintained bike with good tires, good brakes, ABS, with an experienced rider, wearing full gear -> less risk than a SQUID in flip flops on bald tires, worn brakes, and a bike that's been neglected for a decade.
When you say "well if a person chooses to ride drunk, so they clearly don't care about their safety so they might as well not wear a helmet" I see using a straw man argument. You shouldn't drive drunk. Period. Whether a car, trike, bike, roller skates, doesn't matter. It endangers others and I don't believe that's right. If you choose to do so with nobody in a 100 mile radius of you, then go for it, but I think otherwise that's wrong. But it has nothing to do with helmets. I see the connection you are making: it has to do with evaluating risk. But studies show that humans are terrible at evaluating risk objectively. We fear airplane crashes, but get into a car no problem. We fear terrorists but assume nobody is going to mug us unless we are in a bad neighborhood. We happily keep loaded guns in the house thinking we are protected when they are more likely to be used against us in a home invasion situation. And again, because you do one risky thing doesn't mean you take all the risks.
Next, I wanted to address the safety ratings of helmets. If you watch the above videos, Ryan does a very good job of explaining it. But to summarize: DOT rating is more or less bull feathers, though helmets without it are absolute trash for certain. What you want is the Snell rating which is much more stringent. I do feel good about my Snell rated helmet, and I've seen what those helmets look like after accidents. You don't generally hear much from people who got into accidents where they hit their head on the pavement at highway speeds and were not wearing a helmet. I wonder why that is.
Lastly, other factors. What you say makes a lot of sense. Some people have neck problems, some think the helmet is going to impair their vision or hearing. I cannot speak about neck issues, but from what I have seen, some higher end helmets are incredibly light. And studies show that a full face helmet is more likely to prevent neck injury in an accident. If I had a neck injury I would not risk it further by riding without a helmet at all. As for vision: yes some helmets impair vision. Lots don't. I cannot see the helmet when I am wearing it. At all. The face shield is so large that I can see everything. If you really are concerned about it, modular helmets are only marginally less safe than solid full face helmets. As for hearing: good. Your hearing should be dampened by your protective gear. Hearing damage is cumulative and the louder something is the shorter the time before the hearing damage sets in. Some bikes' exhausts are so loud that 15 minutes riding on it will permanently give you hearing damage and tinnitus is extremely unpleasant, cannot be fixed, and only gets worse with age. And it's not just exhaust, it's the wind too. A good helmet, like the EXO-ST1400, protect you from that. For the rest there is ear plugs. Good ear plugs don't prevent you from hearing things, they take out low frequency sounds like highway noise, but let high frequency noise like people talking and car horns through. I can listen to audio books in my helmet with my ear plugs in, no problem, or talk to someone at the gas station with the helmet off. They also make the engine sound nicer: all the annoying road noise is gone and you just feel the deeper base more. Cheapest upgrade you can make.
But the main reason you should wear a full face helmet is because you can cry in public and nobody would know
Again, to each their own, I am not trying to shame anyone for wanting to skip a full face helmet. Just want to point out that the logic behind those decisions is usually flawed. The real reason most people don't wear a helmet or wear a brain bucket is because they think it looks cool and they enjoy the wind in their face or peer pressure/image that certain motor company riders often see. We can try to change the latter perception and it starts by setting a better example.