One reason is simplicity in managing it, reducing government costs. For a middle to upper income earner their overall tax rate would be the same, the income ta

One reason is simplicity in managing it, reducing government costs. For a middle to upper income earner their overall tax rate would be the same, the income tax rates could be adjusted so someone on $100k still pays the same overall amount of tax. Second it is gets rid of the high effective tax rates that low income earners deal with. While low income earners pay low or no income tax, they lose their benefits the more they earn, so a dollar earned could mean up to a dollar less in benefits, which is a disincentive to work. Something that is often missed by the people who say having a UBI would be a disincentive to work.