Focusing efforts on the neediest is exactly what it's being done nowadays. It isn't working so swell, and that's the reason the Universal Basic Income idea is floating.
The truth is that nobody knows how UBI is going to work out, it would be an experiment. So this kind of "studies" are just adding some numbers and pretending that they tell you something. Nobody will know anything till it's tried in some country, and we are not there yet.
The real reason why UBI is being talked about is not the present, but the future. If and when robots take the jobs of half the people in a country, you have to be ready for it or face social unrest. For that situation, where the 1% could have the 99% of the rents, you need UBI or other similar redistribution mechanism, or face revolt and people with torches in the streets.