Should not, because their prices are constantly fluctuating, until you retired perhaps the BTC is just a pile of debris, no longer worth to sell so you will lose everything.
For the short term I admit that it will be risky due to fluctuations, but for the long term, I don't think so. the development of bitcoin shows a positive thing many people around the world are interested in using bitcoin and that is the key to the future growth of bitcoin prices that will make you profitable..
This is true but you did not think about one thing. How old are people that get their pension? Retired people are over 65. Most of them are very conservative, and it will be almost not possible to convince them dealing with BTC, not fiat.