[mxschumacher]

dying from a disease is still a natural cause. Unnatural would be getting killed, suicide, accidents etc.

[goialoq]

The term "natural causes" is a misnomer for "non-human-agent causes".

[Retric]

Not quite, 'Eaten by shark' for example is not usually lumped under natural causes. Even if that's a natural event.

[microcolonel]

It fits the "natural versus artificial" dichotomy. i.e. anything is natural if it comes about without human agency.

[lutorm]

If I die from a lightning strike while hiking, I'm pretty sure that's not counting as "natural causes" either.