I'll buck this here. I used to be ATGATT but it's not really that cut and dry. I think it's all the gear that's appropriate at the time.
My padded, fifty-layered jacket is rugged and safe, but 90% of our riding is not asphalt and it averages 30-40 mph. When we crawl over technical terrain, I'm dying and exhausted far sooner than I ought to be, and I've finally coming to terms with the fact that my performance plummets, which is arguably a worse place to be in.
I've biffed many times, and I keep all of those in mind. It's a constant assessment of what am I doing, what's happened in the past, and what could happen. For me, helmet, gloves, and MX boots for me are essential. Head, hands, and feet are all pretty important to riding. But there are situations where a jersey and mesh pants are better than rip stop and D3O.
I get that the unexpected is unexpected, but it's an optimization problem. Staying safe is as much being at your best as it is preparing for the unexpected.