Sorry but that's absurd!
Having an LLC brokerage account is perfectly legal. You form the LLC, you open the brokerage account, and off you go.
When I was working for Goldman Sachs we had thousands of international customers with LLC accounts, never ever did we have a problem with the IRS, or with any︀ other tax agency. Charles Schwab and IBKR also have thousands of international customers with LLC︁ accounts, again perfectly legal.
I honestly don't know why you keep insisting on criticizing a︂ setup that has been used, and it's being used by thousands of international customers to︃ invest in the U.S. market.
As far as what people do in terms of paying︄ taxes back home, that's not the concern of the Broker, or the IRS. Same as︅ if you open a personal bank account at a bank in Puerto Rico, plenty of︆ foreigners do that. They invest their funds, they make money on their investments, and off︇ they go.
Nothing is illegal about that.
As I've said, contact any CPA in the︈ U.S., they'll be more than glad to form the LLC and open the brokerage account︉ for you in less than a week.
And again, paying taxes back home, wherever that︊ is in the world, is the customers responsibility.
To recap, the benefits are plenty. No︋ CRS, no FATCA, no restrictions on U.S. domiciled ETFs if the customer is a EU︌ resident, no taxes of any kind in the U.S.