Basic rule of any investment: never invest money you can't afford to lose. this is not just with bitcoin, even the real world business that people can swear to you will work, one should never put money into an investment using money they cannot afford to lose, in cases of pensions to people they should not take a pension to put into investments unless the person knows that he has enough money to cover all expenses and always has some money left, in which case it makes sense to put the money in bitcoin in some other high risk investment
for example a person who has a pension of 1000$ per month, so this person has his own house and at the end of the month when he takes the money for 30 days of food, pays the water and electricity bill, pays the employee and is left with 200$, then this person can take 50$ and invest in bitcoin, even if he loses a few dollars something like 5$ and is left with 45$ because the price of bitcoin has dropped a lot still this person will not panic because this person is not depending on the profit of bitcoin for a living, at the end of the day good finance management is the most important thing people need to make good investments
Thinking about a failed investment at their age, so yes, with your argument better not to proceed and just use the pension money to live your life while you are still capable to enjoy with your receive money.
in most casinos people who receive pension are not very old so if they have good planning and financial management they can do very well in the cryptocurrency market, we see people aged 50 or more in this cryptocurrency market and they are successful people, so it is possible for someone pensioner who has good financial management to do well in this market