Even though they are less targeted than conditional social welfare, unconditional cash benefits still predominantly help the poor because they are often hamstrung by transaction costs more than personal irrational behavior.
What makes unconditional cash benefits particularly attractive politically is that they enjoy wide support across the political spectrum. That is because they do not obviously take something away from one group (social, racial, you name it) to give it to another. Of course in fact that is precisely what they do, but they do it in a socially blind manner.