UBI decreases productivity because fewer people will choose to work.

UBI decreases government efficiency because now it has to process sending out checks to every citizen (and some non-citizens, and some dead ones, and some fake ones).

UBI increases taxes because citizens will pay for it.

UBI increases poverty because fewer people will choose to work.

UBI increases crime because more people are impoverished.

UBI increases socialism because that's what it is -- income redistribution, formerly known as theft.

UBI increases the risk of tax revolt.