Before you accept your plane tickets you get asked question about illegal hazards you are flying with. Lithium batteries are clearly noted. Maybe you are just skipping that notice because you assume you are not a hazard? :)
This definitely happens stateside. Usually during check-in
They had to pull my checked bags once because I couldn't find an 18650 when they asked me about carry on batteries for a puddle jumper the last time I flew, which was nearly a decade ago at this point. They definitely care. The passengers are also supposed to care.
People who don't care are the reason I don't fly anymore.
This definitely happens stateside. Usually during check-in