Because the amount of UBI in dollars received will change over time, expressing it as a percent will work. Let's call it UBIC or UBI-Cent for 1/100 of your UBI. Maybe a fully pledged 100/100 UBI would be UBID or UBI-Dollar.
Let's say you have a platform for teaching and learning, and students subscribe to their teachers and peers by literally pledging their UBIC to them.
Within this system, students have a means to live and study using their UBI, and teachers the same. Imagine liking the work your friend is doing, so you pledge them 1 UBIC. Or finding a teacher with a good price to match your situation.
I feel like there is room for entirely new systems of teaching/learning in a society where everyone has their minimum financial requirements fulfilled and is not going to starve.
But even if not - no.
The best scientific breakthroughs were always made because of some scarcity and urgent necessity. Check Turing, history of Xerox lab etc etc.
Laziness and easy life is a bad motivator. Whether you like it or not.