#1) it doesn't pay any dividends like stocks
#2) risk of extended drawdowns which could cause loss of principal unlike in a real estate investment where the property only goes up in value
#3) unfavorable tax treatment since it cannot be depreciated like many types of assets can be when used for business purposes
the fact that it doesn't pay any type of periodic cash flow while it is owned is a serious issue. for these reasons i don't really like bitcoin as an investment.
#1 not all stocks do, plus although you have some portfolio saying you have a stock. its not actually really yours. its just an assignment registerd by the company and the company can dilute your shares without your consent
#2 property value does not always go up.. a house price is X. people pay X+Y+Z where Y+Z is the mortgage interest, state tax and maintenance and years later the market may not even be at XYZ when the person wants to sell. many people buy property but end up getting forclosed on and losing their investment and having to file bankruptcy
#3 there are many tax loopholes, its just education