The corporations need their markets and their sources.
The houses need the corporations.
Don't ever think that anyone pulling out of a house is not a major thing, with major consequences for both the corporation and house.
Those who yell "Oh but they've got this and that".
They don't use them right now. If they did they wouldn't have these issues.
There is a reason they don't use them.
Then there's the failsafe consideration - speculation and the economy.
If Rheinland is seen to be nationalising places etc, people will not invest.
People are easily scared. Look at modern day companies and see how even the failure of a new product can destroy the stock price for a large company.
Imagine if Sony decided to stop selling in the UK. The real damage wouldn't be the dent to their sales, it would be to their stock prices.
Stop waving e-peens and start using your brains. Corporations on Earth are heavily dependent on each other, imagine that but on a far vaster scale.