Age is the main reason. The more the age is increasing, you will noticed that the lesser they use bitcoin. Old people do not like new things like bitcoin as they prefer the old ways they are making and holding money.
Bitcoin is now more than what people can think is a scam.
Not everyone looks at it that way though. I'd say more of ignorance and misinformation, because if you're properly informed on how it works or if someone they know close enough have benefited from it, they will sure have a quick change with how they look and go about it. Finally, we have incompetent set of political representatives doing nothing to get a bitcoin reserve. So unwise!