The government is run by the people. If it increases cost to tax payers over all then the tax payers (people/voters) have every right to oppose this. Even social security alone (for elderly people who can't care for themselves) is untenable, the government has been borrowing from social security funds for decades. Many millennials are at risk of paying for SS their whole lives only to find it can't actually support them at their old age. UBI doesn't make sense at-cost.
The reasonable arguments I've heard state that homelessness, crime, medical cost and similar things will have reduced cost, in which case, sure, why not. But there are a long list of things that need funding long before UBI, if it is at-cost. Another good example is minimum wage, does it make sense to have such a low federal minimum wage and impose UBI on top of that?
