I think the low number is people is due to stigmatisation brought on by government propaganda and the reaction of people invested in property and other assets dependent upon government intervention for their security models (e.g. securities regulation, and police / nimby policies around housing and real estate, direct government liabilities like pensions).

There are many more people who are afraid of Bitcoin than there are who own it, and they use the media and government to make sure people who own it don't shout about it without social repercussions.