>>509490721 (OP)1:UBI would cause massive inflation, meaning the money you are given would pay for less and less over time. Till you get to the point where it only paid for absolute basics. You would not even be able to buy soda.
2:mass immigration, people from all over the world would fight to get into any nation with UBI and bankrupt the entire system.
Many posts you see pushing UBI are made by countries who are enemies to western nations, for this reason.