The biggest problem is that NIT or even UBI is supported by many on the right as an alternative to the "government knows best" spending programs and as an addit

The biggest problem is that NIT or even UBI is supported by many on the right as an alternative to the "government knows best" spending programs and as an addition by many on the left. For someone like me who ends up paying the majority of any social program, the former is a good idea and the latter a non-starter, but politically you'll never find an elected (or even electable) politician who will advocate for replacing existing, entrenched programs with direct cash payments.