If this is the main feature of UBI (guaranteed basic survival), then what's the difference to the current social systems as applied in several western european countries (e.g. scandinavian, french, german, swiss...). A "basic income" is in so far guaranteed that you will always have enough money for a roof over your head and enough food on the table. If your employer truly abuses your workforce, you are able to quit without the fear of becoming homeless and go hungry.