Well the article is primarily about the technical implementation, not the business rationale. But they still mention the main reasons: engineer productivity, community support, and performance gains. All of those translate to money.
As someone who used to work on large Backbone apps I agree that it's a huge drain on developer productivity -- hard to add features, hard to test, lack of standards, etc. Not to mention the recruiting problem: I would never accept a job offer to work on a Backbone app again.