Until we get that Holy Grail of general AI, services are the exact opposite of scalable. Even then, most services will need to be replaced by AI and hardware, which will depend of manufacturing scalability. A single factory can be big enough to mass produce enough widgets for every person in the world but that can't be done with lawyers, restaurants, barbershops, retail stores, or driving instructors until we have advanced robotics, AI, teleportation, virtual reality, etc. at which point it's just software and manufacturing. Just look at how the manufacturing sector output has grown over the decades despite a static labor pool while the service sector employment expands linearly with its size.

More importantly, manufactured goods can be exported much more easily to a growing global consumer base than services (other than software) that are almost always limited locally or regionally.