> Snake oil is actually very useful

You don't appear to actually understand what the phrase "snake oil" means in English. It doesn't mean "snake oil isn't useful".

It means: during in the 1800s Chinese immigrants to American used snake oil (from the Chinese water snake; the one in your link) as a cure-all. Unscrupulous "snake oil salesmen" would sell what-they-called-snake-oil-but-actually-wasn't. Or it used rattlesnake oil instead of water snake oil.

Here's a 90 second video that says the same thing: https://www.youtube.com/watch?v=LaDsOJATX3A