If you give food to somebody who isn't hungry, it gets either trashed or they get fat. Neither are desirable outcomes. It also trashes the economy, since people will have a hard time selling foot when everybody already has some.
It is much more effective to simply give people money to decide for themselves what they need (except for maybe medical care, since getting sick isn't a choice), than having the government try to figure that out for 300 million people at once.
Because you cannot have something as a 'right', if it requires someone else to be compelled to provide goods and services for you. Because then your right to food means that someone else does not have the right to the fruits of their labour.
Rights are something that can be enjoyed by everyone simultaneously. For instance, your right to travel does not mean that someone else has to buy you a car or a plane ticket - all it requires from others is non-interference.
The Universal Declaration of Human Rights disagrees with you. It says
> Everyone has the right to a standard of living adequate for the health and well-being of himself and of his family, including food, clothing, housing and medical care and necessary social services, and the right to security in the event of unemployment, sickness, disability, widowhood, old age or other lack of livelihood in circumstances beyond his control.
Lots of developed countries already have that. But it's not enough because it raises the threshold for being "poor". I live in a poor neighborhood where nobody lacks any of those things but they still go begging for cigarettes in the street because those aren't part of the universal right. People always want more (not judging, just observing).
And that is the big miss I am completely worried about. We don't need a basic income if one year later vegetables triple in price and our income stays the same.
Feel like that has a much bigger chance of going somewhere