Proposals to adopt a UBI raise three questions.
The first is whether a UBI should add to, or replace, the existing safety net. Adding the program is a nonstarter, since the current U.S. fiscal path is already unsustainable.
The second question is whether a UBI would be better than the existing safety set, holding expenditure constant. The answer is probably yes: eliminating TANF, SNAP, Social Security, Medicaid, Medicare, disability insurance, energy assistance, housing subsidies, and more would mean a huge reduction in bureaucracy and a less paternalistic system.
Replacing the current system with a UBI also facilitate repeal of policies that attempt to redistribute by interfering with the price system (minimum wage laws, rent control, anti-price gouging laws, and more). These policies are often poorly targeted and even counterproductive.
The third question is whether a UBI should be a federal program or left to individual states.
Advocates of anti-poverty spending assume it should be federal, believing the state-by-state approach generates a “race to the bottom.”
Government programs, however, almost always expand, so competition between states plausibly promotes a reasonable balance. Many states redistribute beyond what the federal government mandates; California and Washington, for example, have minimum wages higher than the federal requirement.
Eliminating all federal redistribution, while allowing states to operate UBI programs, thus implies a smaller, less distorting safety net that would still protect the most vulnerable.
I agree that the "universal" aspect looks weird. But structuring it that way makes various models or calculations really simple. In practice, the tax code would presumably be progressive, so higher income individuals would still be paying, not receiving, on net.
One possible problem with UBI that I rarely see mentioned is that, unlike Friedman’s negative income tax, it would presumably apply to all citizens (hence “universal”); surely someone like Elon Musk doesn’t need more subsidies than he already gets.