The subsidiaries will always exist - most countries require an employer to be a bona fide local legal entity of the right kind; e.g. an American company cannot have an Italian employee; they can have a self-employee Italian contractor, but not an employee - and the laws of “who is an employee” aren’t that simple (even in the US, as you can see in the case of Uber)

And their existence guarantees that tax burden will be optimized globally, rather than locally - the nontrivial price of setting up and running a subsidiary has been paid, so of course it will be used to get benefits as well.