This is a truism but incorrect in the context of this conversation.
UBI does not increase incomes for everyone. It is a wealth redistribution. Many will see their income fall, especially initially, in order to prop up the incomes of the poor and those who decide to live solely off UBI.
What you're thinking about is a negative income tax or some other BI that is disproportionately weighted.
Many people (the wealthy) will have their net income (income after taxes) go down considerably in a UBI system.
For example, everyone gets $12k a year in UBI income, however funding such a system will require a fairly stiff tax increase (this is how the wealth redistribution will occur), so for high earners, their $12k in UBI will be negatively offset by the increase in taxes.
As an extreme example, someone earning $1MM annually will get the $12k UBI same as everyone else, but an (example) increase in the top income bracket from 39.6% to 60% will cause them to pay $118646.4 more in taxes resulting in their net income under a UBI system to go down (-$118646.40 taxes + $12000 ubi) $106646.40.