Despite centuries of cultural memetic RNA from that foundational insistence on the Protestant work ethic, leisure is not a sin [1], and no attempt at UBI could possibly work if we continue to denigrate it. "They need purpose and responsibility," is an interesting moral judgment born from that. One can find many purposes in leisure, and not all societal responsibilities are encode-able as jobs (there are obvious ones such as housework/chores that capitalism just about outright ignores in salary determination, for example).
The balancing act too between what constitutes leisure and what "job worthy" creative expression/exploration is a fascinating gray zone. Previous works programs did find interesting uses for artists, writers, photographers, etc. But building such "jobs" is to some degree bureaucratic red tape to the creative spirit, and calling it a "job" tends to require progress tracking and discourage creative failures. Similar too, entrepreneurship as a works program "job" would discourage certain types of creative risks. UBI at least has the theoretical hope of allowing people to explore creativity and entrepreneurship outside of the limited job scopes than a works planner might be able to imagine to measure if someone is "working" their "basic job" "well".
[1] Pardon the overlapping secular connotation/religious denotation here, but that intentional dissonance perhaps best illustrates the point. Admittedly, there are still plenty of religious groups that feel that life without work is indeed sinful in a religious sense (what remains of the Pennsylvania Dutch/Amish/Quakers/Shakers/etc), but from a separation of church/state perspective that is all the more reason not to legislate whether or not leisure is a sin in a secular sense. (Leisure can be a great liberty; Thomas Jefferson made sure to add "the pursuit of happiness" to the Declaration of Independence for multiple reasons.)
