People with dependents are one case that comes to mind when considering why this might not be a great idea. Elderly people with no dependents are one example I can think of why this might not be the worst thing in the world.

But in general I tend to agree that there should be some means to humanely end ones own life that doesn't automatically presume insanity. I think there's probably a reasonable middle ground to be had between the extremes of whenever and never.