Kim thought it was unfair for Daniel Byrd to be trapped on Voyager in his place.
Part of his reasoning in destroying the Universe was to save Daniel Byrd from being trapped on Voyager.
COSIMO: Are you so sure? This is a pretty good place for you, Harry. You have a wonderful job with Starfleet, a beautiful woman who loves you. Why be so quick to turn your back on all this? Maybe this is your, er, fate. Isn't that the word your people use? That thing which was meant to be? Hmm? Seems to me you're actually a very lucky man.
KIM: What about Danny Byrd? He isn't so lucky. And Tom Paris? Fate wasn't so kind to him. No, it isn't supposed to be this way. I'm supposed to be on Voyager in the Delta Quadrant. And that's where I have to go.
COSIMO: Very well.
The only way to not have "a" universe leftover in tact with Daniel Byrd not trapped in the DQ was to destroy this reality completely.
FRom DS9 In the Cards.
JAKE: I'm human, I don't have any money.
NOG: It's not my fault that your species decided to abandon currency-based economics in favour of some philosophy of self-enhancement.
JAKE: Hey, watch it. There's nothing wrong with our philosophy. We work to better ourselves and the rest of humanity.
NOG: What does that mean exactly?
There's a labour glut.
Everyone wants to work, but there's not enough jobs, which might be why you get some one like Julian's dad "Dick" who had so many professions because he trains up for one job, but he's ass at it and left sitting on his thumbs because no bugger will contract him.
(I imagine that education is "free", and entrance is purely merit based, even if they make you cage match like Wesley did in Coming of Age to justify the resources that will be expended your education.)
Getting a job in this society is a privilege.
However, I also assume that that Starfleet itself is a sort of hands on polytechnic institute, if you want to wonder about the enlisted ranks floating about. I mean sure O'Brien is a lifer, but what about the people who just sign up for a two to 5 year contract to learn a trade? However in reverse, others could get preferential slots in "schools" of their choosing if they agree to sign up with the fleet for a small number of years, just like how the army and navy these days pay student tuition in exchange for service.