Publishing is generally speculative, and the common perception of "the author" as an ordinary individual with an interesting expression of an idea is inaccurate. A more useful analogue is "student who has just taken out a loan." Non-dominant publishers, meanwhile, bet that the large advances they do give (way too large) pan out into a property that can claw back some market share and cultural attention from major franchises, who should in this metaphor be known less as a copyright holder and more as "the house."

For the general expression of ideas in a corporate setting, copyright is an asset that is backed by a legal team. You're betting that a property gives you a competitive advantage.