When I was a kid, I used to ask why poor people don't just start a business, or go out and get a better job? That was before I understood the way that poverty traps people in a cycle. And the fact that we don't all possess the capacity to become entrepreneurs and creative thinkers.
I think a basic income is most important for the uncreative people. The people who don't really have any talents, and never had any big aspirations. The 50% of all people who have a below-average IQ. Maybe they can't think of something productive to do, but in a post-scarcity economy, why should they need to? When the whole farm-to-table pipeline is completely run by autonomous machinery, then I think there's nothing wrong with just relaxing and enjoying life.
I'm worried that this YC research program might end up making the wrong conclusions, if the results are only analyzed by startup people who are hell-bent on "changing the world" and being ultra-productive all the time. So what if a recipient just chills out all day, goes for walks, swims at the beach, takes some photos, and plays some video games. I hope they wouldn't call that a failed experiment.
Unfortunately this is not the case. What do students who live on student loans and/or parental stipend as a "basic income" do? You can expect more of that when the government becomes the parent doling out the stipend.
Serious answer: besides the ongoing need of the 'elite' for childcare, most proponents of basic income argue that people would not just play video games all day. If you think about everything you or other people might want to do in your free time today, even - how many of those would you prefer to do without simultaneously minding children?