I've never experienced any deaths on hikes, but I have experienced folks suffering the initial stages of hypothermia (and not realizing it) when wearing jeans on a multi-day excursion when the weather went from dry and sunny to rainy, to icey-rain to sleet.
Unwaxed cotton absorbs water, stays wet, and shrinks when wet to make close contact with skin--three properties that one does not want when its wet and cold.
That depends on the specifics of the environment, trail, and your pants.
Indeed, going "pantsless" for short periods can be less risky if your pants are already soaked-through, it's very humid, there's ice build-up, and there's little to no risk of skin abrasion from terrain traversal.
Unwaxed cotton absorbs water, stays wet, and shrinks when wet to make close contact with skin--three properties that one does not want when its wet and cold.