The arguments here are quite much, but here are the three most persuasive I could come up with:
1. It is better to regulate.
It is always better to have some rules rather than not having any at all: legal or not legal, euthanasia will still take place from time to time, so instead of allowing people to break laws and abuse orders, it is better to legalize it or at least make some rules to regulate it when it becomes necessary. There will be better protections for patients if some rules about euthanasia exits today. Patients will be able to initiate the formal procedures needed in regulated euthanasia if he or she fear that there is intense pressure to initiate to euthanasia as the last option. This is never done.
2. It is an individual choice.
Many believe that each individual should be given the right to decide when to die, how to die, and in whose hands to die. Behind all these lies the beliefs that human beings should be given as much freedom as possible, and that any kind of restraint on the right of humans to make choices on issues concerning life and death is a very bad thing. And behind these same beliefs still lies the ideas and beliefs that every human being is an independent entity who reserves the right to make any kind of decision and execute actions based on the decisions he or she has made about his or her life. A strong belief that death is the ultimate end is an ally to this idea.
3. It is beneficial from economic factors.
Euthanasia can be useful for fairness and equity in health resources and healthcare distributions. No government or health authority has been able to push this argument forward. Its inclusion here is for the purpose of completeness.
There is a sharp shortage of health resources in several countries. Due to this, some sick people who suffer very curable ailments cannot access the necessary facilities needed to facilitate their treatments fast enough. Simultaneously, health resources are used on individuals whose sicknesses are not curable, and people who, for reasons best known to them, would have preferred to end their lives in peace rather than live in pains. Giving such people the permission to commit euthanasia would help them get what their hearts desire, and still make more healthcare resources available for treating people with the desire to continue living. The only way to prevent this drug from being abused is by giving the patients with the desire to end his or her life the right to initiate regulated actions and processes of euthanasia that prevent abuse.
You can find more arguments in the link below: