I've worked in the AAA game industry and there are many factors. When you break down the interests of companies this seems like just a product of economic self-interest, financial risk, volatility, and publisher/studio relationships.

But the truth is that the practices of industries are often based on what the employees are willing to take. Employees in the game industry will come back after being fired ... and fired again. They won't quit their job even though they work 80+ hours a week for months on end. In other industries, this would never fly, and practices that assume you can do this to employees would have never caught on, because the employees in (many) other industries won't as consistently take that abuse.

The practices of the gaming industry have, over the years, formed around this fact of nature about the employees. None of it would be this way if employees weren't willing to take the abuse in the first place.