Earlier quoted context omitted.
Most of the monetary requirements are to stop scams - ie where millionaire's kid bills family company abroad for $100K and gets to stay in the US running his company. It's also the reason for requiring qualified investors - to stop this just being family money recycled. Although it is a bit silly that if you invented say a malaria vaccine and had a $Bn in foreign sales you would be deported!
IMHO, it is in the best interest of the US to let rich people in. They have a big potential to invest or consume.
There have been classes of investment visa for people bringing $1M into the country. But then people simply used it to buy a house = $1M in some areas. So then there were requirements that it had to be invested in a business, so people formed a company, bought a house and leased it to themselves.
So the politicians upped the $$ requirement, but that leads to different problems. People with $100M in cash are often not very nice citizens - do you want to give Col Qaddafi, Kim Jung whoever, etc a US visa if they bring $100M of their people's money with them? How many of their family/ friends/ associates also get a visa?