[zmj]

FFI was high priority for C# in the early days, when most meaningful .NET software was running on Windows and doing interop with win32. The runtime was designed to ensure that scenario would be low-overhead, and that legacy lives on in modern .NET.

[neonsunset]

FFI very much remains a priority today which can be seen with changes and migration to [LibraryImport], bespoke NativeAOT modes to produce native dynamically or statically linked libraries which expose C ABI functions with [UnmanagedCallersOnly] and now there is also a project to implement direct Swift library evolution ABI interop for improved support of iOS with MAUI as one of its main goals.