A centenarian relative did this. But it's not actually legal where they lived. So instead of doing it properly, it was done by withholding food and water and they slowly faded over the course of a few days.
It is absolutely insane the way we do this stuff.
I understand why people are concerned about medically assisted death, but this is the sort of thing that happens without it.
I've also seen elderly people whose time was past (very old, bed-ridden, lost their partner) go into into what's basically hunger strike in the nursing home. They said "I'm not really hungry today", eating very little, getting thinner and thinner until the end.
It's now legal here, but family, religion and tradition can be obstacles to assisted dying.
In case you don't want to leave that way, you have to prepare ahead of time. There's different legal means in different countries, e.g. advance directive covers the case where you can't decide yourself anymore.
I think doctors have always pumped people full of painkillers to the point of death long before it was legal. Who would know?
Besides with modern technology it has become debatable what death is. You can plug someone to a machine and keep their heart going for years.
I've heard lots of stories of that being done, anyway. Oh, that much morphine is dangerous, but they're in a lot of pain....