I believe that you were facing the reality of living the 6 months of an agonising slow death in a cancer hospice, you might change your narrow minded opinion.
Which he would be denied, of course, because the best painkillers are "narcotics" and so tightly regulated that it's hard to get them even if you really, really need them.
That's a whole another story, to be sure, but relevant in practice.
I believe it happens, but do you have any sourcing for how often it happens that cancer patients in hospices are denied opiates?
In England opiates used to be under-prescribed for this kind of end of life care. National guidelines were changed to make it easier for doctors to prescribe strong pain relief. http://www.bbc.co.uk/news/health-18169840
(But note: "The NICE guidance is not specifically about end-of-life care but rather patients living day-to-day with chronic pain" generally trying other things before opiates is a good idea for people with long term pain. Exercise and diet and pain clinics are useful.)
And, in this situation: Shouldn't the main focus be on changing hospice care to provide adequate pain relief, rather than changing the law to allow people in pain to be killed by doctors?
(Again, I'm in favour of changing the law to allow assisted death)
I hope you never get to know, or experience such thing, but for some illnesses like cancer, at later stages, even the strongest painkillers don't help with the pain. There are many illnesses which turn you into an immotile person, and if you lack a loving family ready to put up with anything, life becomes a pain no painkiller can relief. Death is a part of our lifes, and our bodies are ours, so I believe we should get to choose what to do with them. If I were to spend the rest of my life in bed, immotile, in need of the service of my loved ones, for years to come, I'd rather put an end, relieve my loved ones from the burden and responsibilities, and my body and soul from the various pain that the situation causes.
All lives are worth living.