Actually some old people doesn't gives interest to what bitcoin is. In my experience, they have difficulty to understand easily the true meaning of bitcoin. So we have to tell them in an easy way that they can easily get what’s the use of bitcoin. We have to show them using our gadgets and be patient since they can catch up on the process of how it works.
The actual reason is that in most cases they are afraid of getting scammed. We can't blame them really. In the recent past, we had a few multi-billion cryptocurrency scams such as Onecoin and PlusToken, which mostly targeted the elderly people. The media also went overboard with these scams. If we could convince them about investing in cryptocurrency, then we may get good response from this group.