I think that letting a foreign entity know about your financial status is pretty "personal", at least for a guy like me it is. Back to the article on point, I remember criticizing the US's need to ask for fingertips from potential visa applicants 12 years ago, in a discussion with my former co-workers. Since then things have gotten worse and worse in terms of privacy (this being just the latest example).

It shows who you've been paying, who's been paying you, how much, and how often.

That basically describes your entire life.