I'm just a single data point, but I'm a "high income" earner who would immediately quit there job if UBI was ever offered.
I'm an advocate for a UBI, and I'd use it to shift from working 5 days/week to 4 or 3 days/week. A move that many argue wouldn't effect the economy's output much at all, considering other countries economies do fine with less average working hours.
Additionally, a UBI would let more people participate in the economy and increase purchasing power of the less wealthy, which would help the economy.
So now I usually just work to pay bills and spending money, stashing away for a rainy day, etc. Most of it goes to taxes.
Given UBI, I probably wouldn't even need to bother.