If you haven't seen with your eyes what a cancer disease can do, than maybe that's the right term. These people are in immense physical pain, so choosing to die with dignity is the best someone can let them do, since they have already lost control over their bodies and obviously - the battle with cancer.
Doing it yourself is no better than dying in pain. If you kill yourself in the comfort of your own home, you are automatically inflicting a huge damage on your family's psyche. Like "hi honey, sorry you're finding me like this, but the society thinks its weird to travel to Switzerland just to kill myself. i left you some money for therapy sessions, since you will certainly develop PTSD after finding my cold dead body in our bedroom". Like... It's sad. Doing it the "legal" way is actually saving the damages that will be caused the other way.
And talking about being a burden, it might not be a burden for the ones that are taking care of the ill person, but he/she will surely feel that way. You don't want to leave this world feeling guilty that you're keeping you family stuck in that situation. You're dying anyway, the best thing to do is convince your family to move on.
We all have our opinions. I don't know what would I do if I ever find myself in a similar situation. I guess it takes balls to take the decision to end your life whether alone or with a bit of help. Either way, it's the sad reality we live in.