The reasons are - Designed around people that might not be familiar with culture, like any (full on 0 social exposure). Basically a person who has scholar skills, can read, understand and read between intentions of words. But anything that's common word or culturally known as is avoided like the plague. - NATO compliance, any nation who bases its doctrine around cooperation with this need to have a copy in their language, some words dont have a translation and coming up with words that follow rule 1 in their language is just a lot of hassle. Keeping to basic "root" words, translation easy. -No misunderstandings, they make sure that each sentence, and word doesn't have any double meaning. Eliminates confusion by giving a very aggressively specific way of wording something. Basically it follows the same layout as laws and statues do, overly specific, so much that it becomes a chore to read. But it eliminates any responsibility by the author of those works. In reality its very much KISS design but they switch the commonly used words with hyper exact ones. Also the reason why they sound weird, because they are not talking to you, the word garble you read is specifically designed in ways to prioritize, first mention important, then details of that important, do not start mentioning other thing until first thing, which important is fully contextualized. Then the second one, then the third one, etc.

Life