The cause of this nonsense is the US courts system.
In the UK (and, I dare say, in most countries) people are expected not to do something obviously idiotic and no-one sues after hurting themselves by doing something daft. Partly out of self-respect but mainly because the courts will send them away empty-handed. For some reason this does not always seem to be the case in US courts and consequently manufacturers fill their manuals with stupid warnings to protect themselves.
The best example of this I remember was the woman who sued McDonalds (not an organisation for which I would normally feel the slightest shred of sympathy) because she had burnt her genitals with hot coffee. She had been driving along with her coffee wedged between her thighs, braked suddenly and then, unsurprisingly, spilled coffee all over her nether regions. This must have hurt but was clearly entirely her own fault but nevertheless, she successfully sued for damages. There is slightly more to the case but this was the essence of it.
The largest section of my car's manual is warnings about what not to do with the battery (viz don't drink battery acid, don't drop the battery on your foot etc).
I have to say that I believe it to be in humanity's best interests that such people are allowed to become the victims of their own stupidity thereby cleansing the gene pool. There are a lot of things I like about the US, but the legal system is not one of them.