The entire *purpose* of copyrights is to get works into the public domain.
No, that is not the purpose of copyright. The purpose of U.S. copyright law is set forth in the Constitution of the United States of America, Article one, Section 8:
To promote the Progress of Science and useful Arts, by securing for limited Times to Authors and Inventors the exclusive Right to their respective Writings and Discoveries;
Now, are you done proving your ignorance?
Shades of privacy concerns, to say nothing of jealousy on the part of established payment system companies that would love to collect such valuable information.
What the author doesn't seem to know is that credit card transactions are itemized. Even if one's bill is just a summary transaction statement, one can request and receive an itemized bill from one's credit card service that will show every item purchased. "Established payment system companies" already collect and keep on record this "valuable information". They have been doing it for as long as they have existed to investigate and prevent fraud.
"Gotcha, you snot-necked weenies!" -- Post Bros. Comics