Interesting question! Google spit this out and it makes sense:

The primary reason these specific keys/issuers were created was to solve data sovereignty and data residency requirements for customers in those regions.

Many European and US corporate clients operate under strict legal frameworks (like GDPR in Europe or various federal compliance standards in the US) that legally dictate where cryptographic infrastructure can live, where data can be decrypted, and who can possess the root or intermediate private keys.

Generating separate regional keys is a compliance mechanism to guarantee that a customer’s data or handshake traffic stays within their jurisdiction.