Because coders are mostly considered to be line workers.
They're comparatively well-paid labourers but their work more often than not is perceived as a cost centre with the actual value creation happening elsewhere (product development, design, marketing).
At least partly, coders have themselves to blame for that. By identifying as a "Java / JavaScript / Whatever developer" rather than someone who solves business problems developers commoditise themselves and their services.
If you're essentially marketing yourself as a set of TLAs you become a fungible resource.
