I think the problem is that CS is too young to have sub-disciplines. If you want to lay a concrete slab foundation, then you get an architect, multiple engineers, the rebar guy, the cement mixing truck driver, the person that understands the chemistry of the cement, dyes, etc. Then, you get the guys with shovels to spread it around. Finally, there are some artisans that somehow make it perfectly level using nothing but plywood, trowels and brooms.

None of those people can replace each other, and they all have different titles / work for different companies. Even the untrained people that spread the concrete around can't be replaced by the others; no one else has enough muscle tone / stamina to do that job!

In CS we have many, many sub-specialties, but we don't have names for those specialties.