> The answer is, because the money doesn’t come with a loyalty oath

But it does come with some reasonable level of consideration and appreciation.

You don't know how they feel, so what you're saying is "they have to show/express appreciation," which is synonymous with a loyalty oath.

The government pays to get good universities which attract smart foreign who come to the US to study on these universities.

Maybe the government should appreciate them not the other way around.

What about e.g. writing an op-ed expressing one's views conveys a lack of consideration and appreciation?

It is their right to be there. They do not have to show appreciation and the current government should never be one deciding these what is appreciation. Bowing to authority is exactly the opposite of what education is about.

Being paid what you're owed doesn't necessitate gratitude.

Why do you think this?

Consider that any competent manager will value polite debate and constructive criticism far more than the empty words of "yes" men.

Guess which category "reasonable ... consideration and appreciation" falls into.

Put another way, if you read North Korean state media, you will find that they always have a reasonable level of consideration and appreciation for their government.

"you didn't say thank you!!!"