We are never going to live in a society which is 100% able-bodied and working-age. A significant portion of the population will always be children, elderly, ill, and/or re-training. Typically, we’ve made the decision that the first line of support should be family, because it’s efficient. A close family member is more likely to know your medical history, will be dedicated to your long-term interests, keeps close tabs on you, can hopefuly tell whether you’re scamming them, and will be more likely to share property communally (i.e. adding a family member to a household does not double the costs of the household). Hence for a full-time income to be sustainably “liveable” it should theoretically support two people on at least a subsistence level. The alternative is to subsidize what I’ll call the “natural nonworkers” directly, which has a lot of administrative overhead and diseconomies of scale.