playing fast and loose with formal definitions here, but basically because services, by their very nature, are scarce goods -- you are paying for someone's time. once you productize/automate that, it becomes non-scarce and the marginal cost falls through the floor.

so, like the whole ideas and sharing flames analogy.

now, note, this does not pertain to products that perform services. that's a whole 'nuther ball of wax. but, in our example, that'd be like cloning the musician rather than the music.