Part of the answer to this question has to do with the culture of Viet-Nam, its traditions, and the way that they interact with both the physical and spiritual world.
In Viet Nam, festivals are a deep part of the culture. As with all other traditions, festivals are often created to give thanks for something, to celebrate something else, or to commemorate a day, or a special person. In Viet Nam these festivals are not just mere celebrations; they are thought o reinforce the morale, pride, and spiritual connection of the citizens. They are a vital part of their identity, and they represent something much bigger than just a "gathering" of people.
According to statistics from Viet Nam's Department of Culture and Information,
[Viet Nam celebrates]...8.902 festivals, among them there are 25 imported festivals, 7005 popular festivals, 1399 religious festivals, 409 revolutionary historical festivals and 64 other festivals.
Moreover, according to Tran Quoc Vuong,
“festivals consists of two parts. The ritual part is offering sacrifices to deities, Buddhas…The gathering part is a crowd gathers in a village or in many villages. These two parts are separate while they are unseparated
This being said, imagine how terrifying it would be to Le Ly Hayslip to live in a world where these very essential activities are devoid of a place for worship. So much depends on these festivals; their celebration is important to bring people together, to safeguard blessings, and to assert the identity of a culture. Judging from the large amount of celebrations altogether, the celebrations take a large part of in the total lifetime of the Vietnamese. To eliminate the conduits of these events would be the same as eliminating a large part of their lives, and themselves.