There's a fixed cost to administer such arrangements.

But the system is not fixed - people do start exploiting these arrangements, and once the number reaches critical levels they get whacked. An example in the UK was "employee benefit trusts", which were used by a lot of celebrities and footballers. https://www.rossmartin.co.uk/disguised-remuneration-zone/302...

You need to be big enough to (a) pay for enough legal bulletproofing and (b) have political cover against the law going after you.

They can't afford a legal department and the paperwork and compliance involved in setting up and maintaining a bunch of international subsidiary companies.

It only makes sense with large amounts of profits to launder through such a system.