It’s the most commonly spoken (Western) language that uses a lot of compound words with and without dashes. I always tend to think there’s a German speaker involved when I see dashes used in English where a native English speaker wouldn’t use a dash, hah.
Storage isn’t nearly as expensive as it would seem looking at normal consumer cloud storage pricing. I think they also clear the cache of truly obscure content after a while. And I also think some of the “cached” content isn’t even stored on their own servers, but is actually streamed from one of the 3rd party direct download services. That would ease the storage and traffic load massively.