If you stored resources compressed, memory usage likely would go up, as you would need (part of) the compressed and the uncompressed resource in memory.
Traditionally, that would be offset by decreased disk usage and faster I/O, but disks are a lot larger and a lot faster nowadays.
Presumably, you would still download these files compressed (e.g. using http compression)
Edit: further Dow, that page is clear that that’s the reason for not compressing chunks:
”A key consideration for efficient direct consumption of usdz files is that, given an archive already held in heap storage (possibly arriving over a network) or as a single file on disk, we be able to use the most direct API's available in USD for accessing the data contained within the archive, without extracting files to disk, or allocating more heap storage. If we allowed either compression or encryption in usdz archives, we would need to violate one or both of the preconditions that allow, for example, the usda and usdc formats to access their data via direct memory access (typically via mmap).
We do not believe the lack of zip compression will be a serious concern for data size. Most image formats themselves allow internal compression schemes, and the usdc format is quite compact, particularly as you collect more data into a single file; although we do not yet have an end-user tool for doing so, USD now contains all of the core features we require to aggregate an arbitrary composition's worth of usd files into a single file, without removing any composition features from the scene.”