Videos still need to be indexed, why would Google keep the videos without indexing them?

Let’s not confuse the videos with the index of the videos. Videos can be stored on the slowest and cheapest medium, indexes might be kept in memory or flash. Each video takes hundreds of mb compressed, an entry in the index could be constant per video

Indexing and storage are two different things. If something if not accessed regularly, then you don't want to index it. You can still access it, it just takes longer to find.

Okay, so the videos may become preserved but inaccessible.