The U.S. Postal Service announced on Wednesday that it will discontinue first class Saturday mail delivery, marking another milestone in the decline of the once-ubiquitous government service. But it isn’t a switch to online mail that’s causing the postal demise — it’sCongress.

Under the Postal Accountability and Enhancement Act, Congress has for years forced the USPS to pre-fund 75 years’ worth of pensions for its employees, a requirement not made of any other public or private institution. That means that the Postal Service is footing the bill for employees it hasn’t even hired yet.

The USPS doesn’t actually receive money from the government, but still needs Congressional approval to make any changes to its structure. An analysis in July showed that the USPS, without its pension requirement, would have a $1.5 billion surplus.

But Congress has repeatedly failed to address the issue. Last year, the Postal Service defaulted on a pension fund payment for the first — and then second — time in its history, and political infighting stopped Congress from bringing any remedy to the floor.

Postal access is, ultimately, a rights issue for rural Americans; since they live in areas where internet coverage is inconsistent, post office closures and slowed-down delivery can mean big limitations on communication. A lack of access to postal services can lead to a growth in economic inequality. The new rules for Saturday delivery, set to take effect on August 1, 2013, will continue delivery of packages, but discontinue basic first-class mail.