food

This goes back to my previous point that traditionally it may not be vegan. The thing about our diversity of culture and climate is that different locations may specialise or adapt a food item to their needs.

If your humidity/temperature of your region don't allow you to successfully ferment tofu safely and consistently every time before electricity, would a brine not be the logical solution? And for some coastal regions in the days before MSG, wouldn't adding dried shrimp (a shelf stable ingredient) to enrich the brine make sense?

Culture is another part of it. I didn't grow up with milk as a common ingredient, but it may be different for other Chinese. Tibetans would probably have (yak) milk on a daily or almost daily basis, Tibetan and Tibet adjacent Chinese may very well have add milk to foods long before Walmart ever existed. Hell, maybe since before The United States of America ever existed. I don't know enough about western Chinese cooking tbh.

But in modernity, adding animal products makes less sense. You're no longer just supplying your village, your product is potentially going to reach Uyghurs, Hui, devout Buddhists, overseas Chinese, etc. Why would you add shrimp skin to the 卤水 brine when MSG is cheaper, halal, vegetarian and doesn't hamstring your export potential? Why brine it at all if temperature and humidity control is trivial in the 21st century?