This is a typical pro-death response.   If your objective is to avoid pain, why not do it at thirty-five or some other arbitrary age?   You want to make it palatable so you avoid the true name of it.   All the pro-death people ask is that doctors go against the Hippocratic oath and  become murderers.  If a doctor does this, he ceases to be a doctor, but a killer.    It is the same way with the killers of unborn babies.   They use the term abortion to make it sound nice, when it is not.  In either case, what you are pushing is death.   You want to make death into this beautiful thing when it is not.   It should not be encouraged in any form.   
Also, no matter how much you might try to outlaw the idea, there will still be pressure put on people to end their lives early by insurance companies and others to lower costs.
http://christiannews.net/2017/06/15/doctor-says-insurance-companies-declined-to-pay-for-patients-treatments-but-offered-assisted-suicide-coverage/