Euthanasia wouldn't change anything for people unable to give consent, and the ones who can consent have options like travelling to switzerland or somewhere else
The problem with Switzerland is, even if you can afford it, it robs you of the precious time that you have left. To travel to Switzerland you have to be well enough to travel, and if that's the case then its likely that you don't want to die just yet.
Take my Dad (and the disease I'm at a greater risk of dying of - genetics suck). Idiopathic Pulmonary Fibrosis kills you by suffocation. Your lungs become so scarred that you can't get enough oxygen and you die. But before that lies weeks and week of being in a terrible condition. You know that feeling you have after sprinting hard and you're really out of breath, you can't get enough air into your lungs? Now imagine that you're in that state 24 hours a day, 7 days a week. Breathing oxygen doesn't help because the reason you're out of breath is your lungs are completely shot. There are no drugs that alleviate the symptoms - painkillers don't help, as its not pain that you're suffering from. Every movement is a huge effort and makes things worse. You can't sleep, don't want to eat and just want the end to come. That's the point you want to go to Switzerland, but you're far too ill to go. So you have a terrible choice to make - you want to avoid the terrible, terrible end phase so you can't leave it too late, but going too early robs you of some of the precious life you have left. The quandry is a terrible one - do I leave it another week? Another week of life, with my loved ones? Or I can't risk being too ill to travel, so I'll end it earlier than I need.
My Dad didn't go to Switzerland. He suffered terribly in the last weeks and there was absolutely nothing that could be done. He was beyond medical help, but not allowed to die. Thanks to crappy genes I may be in that situation in a few decades. If Switzerland is the only option, I'll be the one making that calculation as there is no way I'm going to let myself go through that. Do I lose precious time with the family? Or risk it another week and hope I don't deteriorate.