Security matters. All fintech, blockchain and gambling companies check data of users from all over the world. As there is no unified identity standard, every country define its own requirements on the national level.
There are three types of passport in Cambodia, and all are valid, in Hong Kong locals may have British passports, Australian seafarer's certificates can serve as IDs for their holders.
If a company wants to succeed in passing this minefield, it shall be also acquainted with standard fonts and stamps - and, furthermore, be aware of local peculiarities related to security features of the documents in use. From this point, we start publishing a number of materials on such peculiarities.