There are a few reasons we haven't used the wrapper.

* The larger services require tuning to get the best performance out of zstd, and we use some advanced options.

* We have a "Managed Compression" library which does zstd dictionary compression, which doesn't work with the wrapper.

* We have our own automatic decompression framework that handles many algorithms [0].

* A lot of use cases switched over from other algorithms than zlib.

* A lot of use cases switched over to zstd organically, without our involvement, since it was such a clear win.

[0] https://github.com/facebook/folly/blob/master/folly/compress...