In a perfect world all that you have said above would be fine. But, it's not a perfect world and some people struggle through each day just trying to survive. People get tired of the struggle for whatever reason. And loneliness, to me, is just as much a reason as a debilitating disease.

That would mean homeless people, long term unemployed (unhappy because they can't find work & earn a reasonable income), addicts who can't kick their habit and live a fairly rough life, intellectually disabled people who can't live independently in society, people with diseases such as muscular dystrophy, multiple sclerosis,  would fit in the criteria above - people struggling through each day trying to survive - should they all take the rational suicide option? no matter what age they are?