Yes, I had never looked into this and had assumed Vietnamese uses a Chinese-inspired writing system natively, like other languages in the region. Knowing that this is the only writing system immediately made sense of why this is necessary.
Ehm, like in Vietnam's neighbors Laos (ພາສາລາວ) and Cambodia (ខ្មែរ)? Sure Vietnamese used to (a long time ago) be written in its own version of the Chinese script, I'll give you that. But most languages in the region do not use a script derived from Chinese.
