When I was there last over a year ago, there was a big push to switch logs stored in the internal log service from gzip to zstd. But gzip is extremely well integrated into essentially everything, that it's a little annoying to switch. For example, the base OS images didn't even have zstd installed. It's still worth it for the benefits (at least once all the internal tools started supporting it), but it's not without some downsides. Which is maybe why it took so long to happen in earnest.