The main reason for this would be lack of knowledge, actually I wouldnt call it ordinary, they are just like unaware of what Bitcoin can give to them and in real life scenario, we know there are lot of scams so they are just being careful specially those middle ones as it can make them lose everything in a snap
That is surely the main reason, they always afraid and they don't have money that they can afford to lose, if they had money, why not they didn't invest in the thing that they can see. Just because the problem here is they had a lack of knowledge upon investing in bitcoin. I guess they worried about what they invest and mostly, ordinary people aren't very techy yet and involve in blockchain technology.
We can't blame them, instead let's show them how to manage risk upon investing crypto, From time to time bitcoin will become very popular and even these natural people will surely become interested in bitcoin.