Why don't we use standardized zero-copy data formats for this kind of thing? A standardized layout like Arrow means that the data is not tied to the layout/padding of a particular language, potential security problems like bounds checks are automatically handled by the tooling, and it works well over multiple communication channels.

While Arrow is amazing, it is only the C Data Interface that can be FFI'ed, which is pretty low level. If you have something higher-level like a table or a vector of recordbatches, you have to write quite a bit of FFI glue yourself. It is still performant because it's a tiny amount of metadata, but it can still be a bit tedious.

And the reason is ABI compatibility. Reasoning about ABI compatibility across different C++ versions and optimization levels and architectures can be a nightmare, let alone different programming languages.

The reason it works at all for Arrow is that the leaf levels of the data model are large contiguous columnar arrays, so reconstructing the higher layers still gets you a lot of value. The other domains where it works are tensors/DLPack and scientific arrays (Zarr etc). For arbitrary struct layouts across languages/architectures/versions, serdes is way more reliable than a universal ABI.