If someone doesn't want to live, it is their choice. People can sign a DNR form, which is basically the same thing IMO, so why not have a legal system where people can commit suicide?
I'm not saying it's right, because giving up on life isn't always the right thing and it can hurt those around you. But at the same time people suffer and just don't want to live, you can't make them.
So yeh, it should be allowed, but have a system involved so people can't just go around killing people saying they wanted to die...