Because the Vietnamese didn't romanise their language. The French did.
There have been suggestions to evolve the way vietnamese is written. For example, "Y" and "I" are the same sound, and could be changed to just "I" to simplify. However "Thuy" is a common girl's name whereas "thui" is "smelly". There is resistance to change everything to "I" because it would change the name to something embarrassing.
There have been suggestions to evolve the way vietnamese is written. For example, "Y" and "I" are the same sound, and could be changed to just "I" to simplify. However "Thuy" is a common girl's name whereas "thui" is "smelly". There is resistance to change everything to "I" because it would change the name to something embarrassing.