However, potentially UBI does more than you imagine. There are measurable differences in both behavior and development when meeting basic needs is a struggle. Rutger Bregman did a great job touching on some of the basics in this TED talk: https://www.ted.com/talks/rutger_bregman_poverty_isn_t_a_lac...
By giving low income people extra cushion (even a small one) you can improve their cognition and decision making, giving them a platform from which to improve their lives, pursue education, even innovate. All without complicated, difficult to implement and expensive social programs designed to achieve the same goals. Poverty squanders potential.
And then, of course, there is the oft talked about, and in my opinion self evidently valid, concern about an increasing number of white collar jobs being replaced by automation. At some point we'll have no choice but to come up with a solution for a shrinking pool of unskilled or semi-skilled jobs.
Conveniently the same process that will remove those jobs, will also make the production of the goods and services they relate to dramatically cheaper. UBI gives some of that surplus to the lower and middle classes, which is important given the danger that it would otherwise be absorbed by the rich.