Also, I'm not sure what 'muh morals' is supposed to indicate here, other than 'a shorthand for any or all of the various reasons one might have qualms about assisted suicide'.
Because, like opposition to abortion it is moral grandstanding. You aren't offering a solution to a very real and very tangible act of suffering that a human being is going through and requires release from. Instead wheels are left spinning; you doubt the intent of the state, you doubt the intent of the family, you doubt the intent and the state of mind of the person who is suffering.
Instead you elevate (and even you do this) the physical over the psychological. Is a man the sum of his thoughts, or the vessel in which his thoughts reside? What are you preserving, what are you protecting and defending him from. Himself? Is that your responsibility?
Why should someone be forced to live with intractable pain, whether physical or psychological? And if it's not moral grandstanding, could you go to someones bed and look into their eyes and no matter how much they sweat, or cry, or shy from touch, of if their heart pounds or their concentration wanes, could would tell them 'no'? It's inhuman.
And if you were the master of this, if you were in some position where you held the power of life and death in a nefarious manner, in a controlled situation, in a time of war or battle, what sort of torturer would you make? Would you be the one who lets them die? Or would you be the one that only stops at death?