Uhh, this is private property, the result of individual households setting aside a portion of their own wages to save for the future. It is not politically feasible for the government to seize private savings it had said were previously for your retirement.
What you want is a defined benefit federal savings program (like social security), but that needs to be funded by taxing incomes, not by seizing existing private retirement savings. Some nations have that and others don't, but it's not a sovereign wealth fund. Please don't confuse the two issues being discussed.
The first issue is whether the government should tax the economy and pay out fixed retirement benefits for everyone, or whether it should promote individuals saving for their own retirement, or some hybrid of the two. This decision has nothing to do with SWFs. Australia has a hybrid system, where households are expected to save for retirement but there are also welfare programs for low income people. Most nations follow this model because it is what the public supports politically and it makes a lot of economic sense.
SWFs, OTOH, are created when a nation gets some unexpected windfall that is short lived, and it wants to smooth the life of that windfall into the future. That is why you invest. Otherwise when the oil runs out, Norway will face a shock. This way, by transforming the oil into investments, Norway can provide a stream of benefits that lasts longer than the oil. That question of transforming benefits across time for the government has nothing to do with whether the government provides defined benefit retirement plans or not for households. This is because even though every household has to plan for retirement when it earns no income, governments do not need to plan for a future when they earn no tax revenue. It is only when you get these predictable revenue bumps, such as discovering you are sitting on a pot of oil, that create a need for the government to smooth revenue across time.
Now Australia does have mineral resources and it even taxes the extraction of those resources just as Norway taxes the extraction of oil. But in Australia, the extraction of coal and iron results in a much smaller surplus spread over a much larger population, and so Australia's mineral wealth, while large in absolute terms, does not support the same level of surplus income per person as Norway's oil wealth - which is not to say that Australia's economy is less dependent on extraction than Norway's. Australia is very much dependent on all the jobs that mining creates, but that is not surplus income, it is income that has to be earned with labor. Therefore when Australia's coal and iron run out, it will be a big shock, but there is nothing Australia can do to smooth that income out, since it's not surplus income. This is why Australia does not put the fees obtained from mining into a SWF - they wont help!
Therefore Australia uses the proceeds from taxing mineral extraction for general revenue, it does not put the money into a special SWF pot, whereas Norway does. Just as Canada doesn't put the money it obtains from selling trees or rocks into a special pot. That decision to not stretch the revenue across time has nothing to do with whether the government has a defined benefit retirement system for households.