This seems like a critical component. In the US or Canada, there is no "old money" in the European-magnitude sense.
In the UK, on the other hand, there are a lot of structures that seem to straddle oligarchy and democracy (see: accuser burden of proof libel laws mentioned in article). There are not just different options for ultra wealthy, but experienced options, staffed by people who have been doing this for decades, at firms who have been doing this for centuries.
Opaque South Dakota trusts look quaint against that depth of historically-earned competency.