The general libertarian argument for a UBI (or NIT, which I favor) is that a sufficient guaranteed supplementary income allows for government programs like the pension and unemployment benefits to be replaced, removing the need for large administrative bodies making sure money goes only to those who meet the entitlements. The rationale for minimum wage also rests on their being a minimum amount of money needed for survival and a maximum number of hours in which to earn it; if people are no longer working these jobs in order to simply survive, the need for a minimum wage is lessened.