Because between us and they have gap about generation 
In fact, older people always have a lot of worries and I do not think they are interested in investing in Crypto because they are afraid because Crypto is so new and it's like a virtual thing, they can not see it and can not handle it. In addition, Bitcoin have a huge risk and it is not valued by any model and fears that this is a psychological game.
I have met many old people and I told them about Bitcoin, as a result I was scolded for daring to believe what the internet said, oh my gods @@