Depending on the circumstances, one of the reasons why may come down to certain regulations outlined by CIFUS[1] or similar inter-government agencies.
I realize you're talking more about individuals, not necessarily who owns a company, but if we were to suppose that a non-US citizen were to become an employee of a company which works on some specific field ("critical technologies, infrastructure, sensitive data, and specific real estate deals") and that foreign employee was promoted to higher and higher roles, eventually being put into a position to hire other people from their country, that might trigger automatic CIFUS oversight review.
It's not enough to simply have a company deemed as critical to be US-based; if the majority of its workforce is foreign nationals, that is a security (and economic) concern for the entire nation, and will come to attention of the US Government.
Dealing with any US government bureaucracy is exhausting, but dealing with US government bureaucracy as it relates to national security is an entirely different beast.
I also realize that "90% of US-based companies" might not currently fall under CIFUS oversight, but if a company expands or pivots into new markets, I would assume that the vast majority of US CEOs would not want to lose out on the opportunity to win an sweet Government contract - that would limit future growth.
[1] https://en.wikipedia.org/wiki/Committee_on_Foreign_Investmen...