Earlier quoted context omitted.
Because of how they utilize that money. The poor will spend it, because they need to. The rich invest their money since they do not need it all. Those investments are continuing to grow. Even if you transfer some of that money to the poor, they are spending it where? At Amazon etc...
The money has to come from somewhere. Assuming we're not completely stupid about it, the rich will pay more in new taxes than they'll get back from UBI.
Except the fortunate rich who own the housing that the UBI beneficiaries will pay for.
I can see UBI making a few people very, very, wealthy.