>>For the same reason that, say, transferring your wealth from an Irish bank account to a German bank account doesn’t trigger a capital-gains event in the US?
If there's a currency change, it absolutely does trigger a capital-gains event, unless you have a truly terrible accountant. Just like when any other asset is disposed of, the value is calculated at that point. If you move USD from one bank to another that's different, but try to move USD - EURO - CAN - USD and you'll absolutely be taxed on any gains that happen (if they catch it).
I think you're talking about currency changes that happen by moving around within US banks, or by moving money between countries where one of those countries is the US or has a specific treaty supporting US foreign taxation.
If it wasn't possible for a US entity to move money between (at least a few) countries that aren't the US without paying US capital-gains, US corporations wouldn't love holding money in Ireland nearly as much as they do. :)
Two things on that: first, moving money between banks but in a single currency wouldn't generate a taxable event - there's no possibility of profit or loss like there is with a currency exchange (i.e. you're not buying euros and then selling them, you're just moving dollars). Second, all the Irish and Dutch craziness relies on multiple corporations (all owned by the parent, of course), which complicates the tax situation a bunch.
If there's a currency change, it absolutely does trigger a capital-gains event, unless you have a truly terrible accountant. Just like when any other asset is disposed of, the value is calculated at that point. If you move USD from one bank to another that's different, but try to move USD - EURO - CAN - USD and you'll absolutely be taxed on any gains that happen (if they catch it).