Why do Vietnamese names sound so simple and repetitive compared to Chinese names?

Vietnamese names don’t sound simple nor repetitive, even when compared with its Sinospheric counterparts such as Mandarin, Japanese, and Korean, since Vietnamese has much more sound combinations than all three of them.

However, if you’re referring to why Vietnamese names in general are repetitive, as in a lot of people having similar names, then that’s due to the lack of Chinese characters.

In the past, names are based on Chinese characters, and these characters are chosen based on their meanings. This means much more random and unpredictable sound combinations since they’re chosen semantically, not phonetically.

But in modern times, when Chinese characters are effectively abolished, semantics is no longer Vietnamese priorities when choosing names. Instead, they’ll choose names that “sound good.” These names usually have nice meanings, such as “healthy,” “lucky,” “beautiful,” and others, but they aren’t really as varied as before. Also, most Vietnamese have similar surnames, so that also adds up to the repetitiveness of name choices. A lot of Vietnamese also continue to retain the middle name convention traditionally shared by Chinese and Koreans, where everyone from the same generation within the same clan shares the exact same middle name, only with a different first name (technically though, East Asian middle names aren’t really middle names, but are part of the given names, but I’ll just keep it as middle name so it makes sense for English readers).

A limited variety of surnames, generations within the same clan sharing the same middle names, and a limited amount of given names due to the lack of Chinese characters limit the diversity that Vietnamese names can achieve, which ends up being quite repetitive.