One of the reasons of this is the inflation: it is a kind of regressive tax, this tax is paid mostly by the poor because they loose their savings, while the wealthy keep their savings not in money but in assets.
Isn't the reason that rich people invest in various assets simply because they have enough money for their daily lives and can afford other ways of investing? 
Give a poor person bitcoins or other assets, and the first thing he will do with them is sell them.