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Please note that the article is quite old and does not encompass the wide variety of scenarios C# is effective at.

Structs are used for but not limited to: all kinds of "transient" data containers, pass by value semantics, precise control over layout of data in memory, low-level programming and interoperating with C/C++, zero-cost abstractions via struct generics (ala Rust or templates in C++), lightweight wrappers over existing types, etc.

Most C# codebases use them without even noticing in `foreach` loops - enumerators are quite often structs, and so are Span<T> and Memory<T> (which are .NET slice types for arrays, strings and pretty much every other type of contiguous memory, including unmanaged). Tuple syntax uses structs too - `(int x, int y)` is `ValueTuple<int, int>` behind the scenes.

.NET has gotten quite good at optimizing structs, so the more general response is "you use them for the same things you use structs in C, C++". Or the same reason you would pick plain T struct in Rust over Box/Arc<T>.

Intro to structs: https://learn.microsoft.com/en-us/dotnet/csharp/language-ref...