for my mother and grandmother, having to shower, toilet, sponge bath, feed, medicate, clean up vomit etc. was very undignified.
they were both very proud, strong women (especially my grandmother) and it was humiliating. she would constantly cry because of this.
it is not the act of dying from a terminal illness that is undignified, it is what comes with it (and not all people experience these things). but for those that do have illnesses with these symptoms/side effects it can be undignified, embarrassing, humiliating....
for me i would want the choice to avoid putting my children through watching and taking care of me in this situation.