People can already get comfortable living an "easy" life of party and shitty jobs till a child happens and then they're screwed.

Worse than that, lots of people have no choice, they inherited no capital and thus can't afford to educate themselves to get a good job since they need to work to supply for themselves and their families, effective UBI would give those people breathing room to work/study what they want and actually achieve enough to have a good family.