I think you're close. A company should never do secondary business X if their proprietary take on X does not contribute to their value proposition in a way tha

I think you're close. A company should never do secondary business X if their proprietary take on X does not contribute to their value proposition in a way that external solutions cannot provide. At one time, for example, ice companies did their own deliveries because they needed special hore-drawn carriages to keep the ice cold.