Hey Joe, let's introduce you to just some basic economics.
The price of goods is proportional to the demand placed on those goods.
Flooding the market with additional currency may seem to work in the very beginning; however, very quickly the market actors selling tangible goods will account for both the increased demand and increased monetary supply, resulting in higher pricing.
The end result will be ever-climbing prices of goods, with ever-higher UBI being printed to chase those climbing prices.
TL;DR: Supply and demand, bro. Read a book.