Portability is nice. I’ve seen so many people in government just trying to ride it out until they qualify for the pension. They don’t really care about the job and are just trying to avoid having to do anything until it’s time to retire. Long-standing structural problems just get covered up and ignored for the next chump to deal with.
It also represents a huge tax on people who want to be able to change jobs. I would prefer a world where people feel more free to leave jobs that suck or aren’t good fits for them. Locking them down with pensions, options plans, or 401k matching programs that vest over time are all mechanisms for employers to recapture what would have been paid out as wages from employees who leave early (who often tend to be younger).
A UBI that puts you somewhere above the poverty line supplemented with a forced savings program seems like the best move. It gives you portability, simplifies the system and administrative burden, and offers a hedge against the vagaries of the market.