One of the rationale for it To me comes from amartaya sen theories, as he lived through some famine in his youth, and studied the phenomena to come to the conclusion that famine rarely happen because of food shortage, but often because of an economic sectors collapsing leaving thousands or millions without access to food whereas food level are still the same.
The logic of everyone must work is sound when one need to work hard to already provide for himself and his familly, but in modern industrial society, one person working with modern tools and technology can provide for hundreds of persons.
This trend can be seen in farming, 50 years ago, 70% of population were farmer, now even 5% over produce, and only a tiny fraction of the population can produce enough food for everyone else.
The solution is opening new markets, new sectors of production which des easy in the 70 with all the new advances in different sectors.
But now, there is no major new market opening, and each sectors produce already more than enought employing only a fraction of the population.
The paradox of today is we dont have lot of poverty because we dont produce enough, all supermerket shelves are filled, we produce cars, plasma tv, smartphone, food, clothe and everything like never before, yet it still leave large portion of the population in poverty, and we dont really live in scarcity at global scale, we dont need to produce more, even on the contrary taking ecological factors in account, it can easily be seen we already produce too much, without requiring 100% employement.
RE: Objections to Universal Basic Income