Why do components only allow primitive values

I’m interested in a technical reason why a component in ECSx only allows for primitive values like float, atoms, etc and not something like structs or tuples. For example, rather than a PositionX and PositionY as separate components, instead have a Position component that stores both x and y coords. I feel like there’s a technical reason like something to do with how ETS works or something but I couldn’t find anything in the code, docs, or blog post that gave a clue and it’s piquing my curiosity.