I think the question is really about cognizance of the risks associated, for both sides.
ATGATT is really helpful in reducing injuries and risk of death during a crash of any level. It reduces, but doesn't eliminate. There are obviously situations where ATGATT just makes cleanup easier (I'm thinking head-on with 18 wheeler, etc).
If someone doesn't wear gear thinking they just won't crash or it won't be serious (just some rash, etc) it is very wrong-headed. Squids are here, as well as some pirates.
If you don't wear gear because you don't want to, but you know damn well that if you crash, you will likely suffer severe injury, that was avoidable, it is fine. People make their own choices, and so long as they are informed, I will respect that. My dad will not wear a full face helmet (my mom and I bought him a nice 3/4 with a face shield) or armored pants. I got him a nice, armored jacket to keep him from wearing a plain leather jacket (non-motorcycle specific: thin-ish leather). Its his choice, and it is very informed: he worked in the ER in south San Francisco for 15 or so years. He's seen what happens. Amputations from impact, the works. He is also very conservative in his riding.
I wear gear whenever I am riding for the purpose of riding, or fast, or long distances, or in riskier situations (traffic, at night, etc). I have a zippered together set of armored jacket and overpants, all made from thick leather. I've worn it in everything from 37 degrees to 115 degrees. If I am just riding around town, I will take my risks without the pants, but usually wear the jacket. I figure: bicycle speeds, bicycle injuries (and I've had some pretty fast crashes on bikes. They aren't fun). I still almost always wear a full face helmet. I feel very uncomfortable without a helmet (and I have ridden without one before).
I carry a half helmet on my bike (its all that fits in the side-cases and on my big head). If I need to pick up my girlfriend somewhere in Berkeley, I give her the gear, and my helmet. I'll wear the half helmet. She's pretty, and I'd like to keep her that way.
My uncle won't even wear a beanie helmet, unless it is mandatory. I suppose that's his choice, and he doesn't ride aggressively or in traffic (Cruisers: A Guzzi California and a Road King), so that's less of a risk.