Chiu heh lo

Tap toi in HK, ho jing siong.

Dialect is hard to preserve because it is not taught formally.
That said, it doesn't mean that it shouldn't be preserved.
You lose the dialects, you lose a lot linguistic flair and fun.
I only speak mandarin, because it is just the main stream language taught to Chinese, I have no attachment to it or feeling for it. My dialect is hakka, and even as shit as my mastery is, I still encourage my children to speak it by speaking with them.

The point is convenience and the utility of mandarin both for commerce and research.
For chinese schools it is about education not about dialect pride, otherwise there would be hokkien and Cantonese schools.
Chinese schools existed before Mao and Nanyang is probably one of the last bastions of pre Mao Chinese culture.