> I don't see how child benefits and state pensions need to exist if you have lifelong BI.
State pensions need to exist as long as you expect state workers to work for (pension excluded) below-market compensation for the jobs they do. BI has no effect on this one way or the other.
> Sure, you could convert state pensions in the public sector into a voluntary retirement fund but the basic idea behind pensions is that the government gives you money in old age so you can afford not to continue to work
No, the idea behind pensions is that, as part of the exchange for work now, you accept a deal which provides payment later (including specified contribution of the funds from your nominal current income, as well as the rest being contributed by your employer.)
State pensions need to exist as long as you expect state workers to work for (pension excluded) below-market compensation for the jobs they do. BI has no effect on this one way or the other.
> Sure, you could convert state pensions in the public sector into a voluntary retirement fund but the basic idea behind pensions is that the government gives you money in old age so you can afford not to continue to work
No, the idea behind pensions is that, as part of the exchange for work now, you accept a deal which provides payment later (including specified contribution of the funds from your nominal current income, as well as the rest being contributed by your employer.)