My friend's question is quite insightful. In the current regulatory system in the United States, securities assets (such as stocks and bonds) are strictly regulated by the SEC and need to be traded on SEC registered exchanges or ATS (Alternative Trading System), with a registered custodian responsible for custody. Non securities assets (such as BTC, ETH, etc.) do not fall under the direct regulatory scope of the SEC, especially for compliant cryptocurrencies, which can only be used when applying for ETFs