[Brockenstein]

It's not unreasonable because everyone understands the state things are in. Once upon a time atom was meant to be descriptive, and time has proven that original description insufficient. We could call atoms something else to address this, but it seems like we've decided "atom" stays, its meaning has just evolved over time in specific usages.

This reminds me of how the prefixes we use in computing hardware aren't right either. Your PC might have 8 gigabytes of RAM, but it doesn't literally have 8,000 megabytes or 8 billion bytes, and the same problem with mega- and kilo- too. Somehow we manage and when we're talking gigawatts giga means 10^9, and when we're talking gigabytes in computing we know it has a special meaning, 2^30.

Same prefix, two different usages depending on context. The only thing I can promise you though is we're never going to adopt gibi, mebi and kibi, at least not in my lifetime anyway.

Understanding the history and evolution can be interesting or informative as to why things are the way they are. So yeah, one upon a time "sub-atomic" would make no sense, it makes sense not of course. We're familiar and used to the idea. Wasn't always the case though.