The question asked about the ethical and moral implications of euthanasia, but that approach may be premature anyway.
Legal euthanasia has been gaining ground in some countries in Europe lately, and what happened is that doctors given the right to end a life under certain conditions that the average person would consider sensible, merciful, etc., have gradually been deciding who should live and who should die, depending on their own personal judgment of the value of that patient's life, not in accordance with the purpose of the law as it originally was intended.
"Well, he's old and doesn't have any friends, so...." or "He's only going to live a few more years anyway and is costing his family a lot of money for his care, so...." is inevitably going to take over if such a decision is put into the hands of attending physician or hospitals.