Homo Sapiens is obsolete
I'm startled nobody talked about that in the comments.
That is the real issue behind this UBI idea.
We have had revolutions: the agricultural revolution, the industrial revolution, but the next revolution ("digital") jeopardizes what makes the difference between homo sapiens and the other living creatures: intelligence.
A.I. boffins speak of an inflexion point called "the singularity". It is the point where the machine will outsmart mankind. Knowing that IQ progresses very slowly (if any at all) and that machines still more or less follow Moore's law, this "singularity" is said to be between 25 to 50 years in the future.
At this point, what will the society do with all those obsolete person?
Of course there are other alternatives than UBI, but that scares me even more!
For those who understand French, I can recommend the speech Laurent Alexandre gave at the 2017's USI: https://www.youtube.com/watch?v=o3WOPKNvbt8
His alternative is transhumanism.
Frankly, having a chip inside my brain is not what I would vote for when we discover everyday the dark actions happening all around, the last one being Intel stuffing a spyware in every CPU...
So pick you choice, between having my brain "enhanced" by Intel/Google or UBI, I'll vote UBI.
Welcome to the scary future!