Euthanasia should be illegal in the United States because it is against the Hippocratic oath that doctor's take when they graduate medical school and become a doctor. It is the responsibility of the doctor to save lives of patients not take them. There are new advances in medicines everyday so there could be a cure for a terminally ill patient.
Euthanasia is not decided by the doctor. It is decided by the family to allow the patient a quick and painless death rather than constant worries and hospital visits. Although not recommended, euthanasia is sometimes best for terminal patients because a lot of the illnesses are not able to be cured but put dormant. There is always a risk of problems and the medicine can both fail and be a waste of a lot of money.
The family may want/decide to have the doctor take the patients life to stop the suffering, but the doctor has to have the utmost respect for human life. Euthanasia is morally wrong and there is a reason doctor's have the oath in the first place. Euthanasia brings a moral burden to the doctor and the family because they have just ended someone's life unnaturally. The cure for the person's disease could come out the next day and the family members and the doctor would feel terrible.
First, it takes over 10 years to create vaccines for normal illnesses. Terminal illnesses are much harder to find cures for and may never find cures for some. The question is not on morality of the subject, rather the choice whether or not to suffer through a painful illness.
It may take years to create a cure, but medicine still advances. They have found ways to slow some terminal illness down. For example, Multiple Sclerosis is a terminal disease, but it has many drugs that slow down the progression of the disease which therefore gives people more time. During this time researchers may find a cure and that person can go on continuing their life instead of ending it. Morality may have not been the right term to use but there is a psychological shock to the doctor.
Even thought doctors can slow down the effects or sideffects of an illness, a person still might not be able to live to see the cure of their illness. Also, most families that due result with the euthanasia as a way out for a person's illness, is determined if the person is living suffering without a chance of getting better. To say that a doctor might suffer from psychological shock from doing their job is not an excuse because soldiers get ptsd's and they just live with it.
First of all soldiers who have been diagnosed with ptsd have it way worse than the doctors preforming Euthanasia and should not just have to live with it. Second of all the person may live to see the cure we never know until the cure is found. While I agree with your point about the suffering who knows that they won't have a chance to get better in a day, week, month, etc. we just don't know. It would be devastating to put a family member to death and find out a week later there is a cure.