No, investing in the older age can and is even necessary. Firstly, do not forget about your family and children, who then can not be in anything because of your investments, and secondly, you yourself can live well and allow yourself all the joys of life
For older age it may be little risky investment as btc prices fluctuates a lot and even falls badly. SO may be older people may not be able or want to take such risk which can erode their capital and can cause problem if they have limited money .