The retired people should take care of their life with the money left with them because in today's world, even your own son may kick you out any day and you will suffer without money. Investing in crypto at that age is for those who have enough left on their hands and want to gift their grandchildren with some crypto later when they grow bigger.
Retired individuals can use their money in any sort of investment but should not use whole pension fund in a single bitcoin because of volatility in its worth. It is true that in present age no one care about one another even a children will left their parents if they don't need them and have no benefit from them because everyone in this era thinks about their benefit.
If one who wants to make investment then he should put some amount of pension fund in bitcoin so some amount of pension he can save in bank. Everyone desires that their children lives a happy and satisfied life so those should save some amount for their children in form of bitcoin or any other asset which he thinks that it will gives huge profit after some years.