Why won't the mainstream media tell the truth about why the US Postal Service is cash strapped?

Yes, the rise of the Internet has meant that what once went only by mail now often is sent by email or delivered electronically. But that is not a difficult problem to manage. Reduction in workforce by planned attrition handles that challenge. Yet this canard is the one and almost always the only reason given in Mainstream Media’s right-wing slanted coverage of the financial challenges facing the post office. They never bother to mention that the real reason the USPO is racking up billion dollar shortfalls is a law Republicans pushed through Congress when they had full control, requiring the Post Office to fully fund retirement and pension funds for all postal workers for the next 75 years in just 10 years. This is on top of Congress excluding the Post Office from competing in dozens of services that could generate significant revenues and that people walking into post offices would definitely want.

Why won’t the press do their job, and actually investigate stories instead of regurgitating political talking points handed to them by Washington press corps commentators who are actually more political operatives than reporters?