1, historical legacy: Tudou, as an early video sharing website, has accumulated a large number of users and content during its development. As an early version, the old version of Tudou has certain historical value and legacy functions, so it can still be used.

2. Compatibility: Although the new version of Tudou has been upgraded and improved, the old version of Tudou is still compatible with some old devices or browsers. This means that some users still need to use the old version of Tudou to access certain functions or content.