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It sounds bollox when someone uses it to express great losses

Why? There are lots of words which can have different meanings depending on the context (which includes who is using the word). Being aware of context and semantics is just a part of communication.

So, you and I both know this thing about the original use of the word. For years, though, people who never knew that thing have heard the word and reused it with a more dramatic meaning, to the extent that it's by far the most common usage. Personally, I just pay attention when I see/hear it in use and would think carefully before using it myself (probably wouldn't because there are other ways to say it that don't risk confusion). But for some people, it's a (completely pointless) hill to die on. There's nothing wrong with the newer meaning, it just happens to have a different emphasis to the meaning some of us have learned from history books about a long-dead practice. Getting upset about it is like being the kind of person who, when an esoteric word crops up on Q.I., feels the need to tell the whole room "I knew that!" and has a fit because when other people hear him use it from now on, they won't think "Oh, how clever he is because he uses clever words!", they'll think "He heard that on Q.I.". In reality, though, they'll just keep on thinking he's a precious cunt.

FFS, even the people who know the original meaning and don't mean "reduced to 10%" when they use it are probably using it to indicate a reduction that's not exactly 10% and if you care about the value you'll want to check anyway.

It's a lost battle with no purpose.

@markyp The "light years" thing is different. It has a practical, current meaning and there might even be times when you can usefully clarify the misunderstanding, although people who don't know that "light year" is a distance are very unlikely to use it to describe time anyway (outside of conversations about science fiction where most things aren't remotely real or even vaguely realistic, so...)