Middle class people already have the equivalent of UBI from their families. Not only do they still work, they are more productive and pay more taxes than people without that support.

My parents provided me with free housing and food for over 20 years with no strings attached. They never told me to get a job or to help pay the bills. While my less fortunate peers wasted their lives working at McDonald's, I had the privilege of being able to study and experiment with different careers without needing to worry about food and shelter.

Behind every highly productive worker is hundreds of thousands of dollars of FREE support that they did not work for or earn in any way.

The only problem is that how much support you get depends on what family you happen to be born into. When the government provides that support instead, it means everyone gets equal opportunity and it doesn't matter what family you come from.