The other issue is the game industry is pretty much the only entertainment medium that has a single source of potential profit, which is the first 90 days of release.
Compare that to movies which have box office, second box office, bluray/dvd sales, streaming, premium cable, cable, general tv. all of these give the product a revenue source.
Books have hardcover release, paperback, trades. not to mention options of the work to film/tv.
music is probably the closes, but then you have cd/mp3 sales, streaming, radio, and licensing opportunities. bands typically make most of their money on tours since that is a controlled cost with high return merch (that $30 shirt was $3 to print).
Compare all that to games. The store. That is it. That is the only way for the developer or publisher to make money on the product.