People using Bitcoin as a retirement plan could be better than most investments out there that people use for retirement but later fail them, for countries with good systems, they can use landed properties and other assets as their fall to plan for retirement and they will receive it without any stress but for people living in countries that the laws can be broken easily and they won't get any repercussions, having your retirement pans on Bitcoin that is a digital and can be accessed quite freely is actually a life saver. With Bitcoin you can save down millions and it won't have any taxes attached
Well, you will actually have to pay tax when you convert it to local currency, or if you live in a country where there is a wealth tax and you exceed the threshold. Another thing is that with bitcoin it is much easier to hide it and transport it, and therefore, if necessary, you can go to a country that has no or much lower taxes on bitcoin. If you have a house worth 1 million dollars and everyone sees it, when you sell it you cannot avoid paying taxes on the sale, nor can you avoid paying property tax while you have it, nor can you take it to El Salvador or any other place where you will not be taxed.
For me, bitcoin should be part, although not exclusively, of a good retirement plan.