because in reality, just like the bullshit of "VOTER FRAUD!!11!!!1!!!!", there are only a tiny tiny fraction of employees "misusing a government credit card". It's all a manufactured thing.
I traveled ALOT during my career (not just down to D.C. metro and back but to at least 17 other states for various training courses and conferences) - meaning all around the country, and if anything, the extra time needed to deal with cash in an office (maintaining/tracking outlays, ensuring the cash is in a safe with a log of safe entry, need to periodically go to the bank to get more, etc) made it WASTEFUL. And let's not talk about the occasional fiscal person "dipping out of the till".
Copies of the monthly credit card bills were sent to BOTH the employee and the agency's local Administrative Branch official, so they were aware of every transaction.
For people in my agency who went overseas for 2 - 3 week trips, which included going to multiple countries (as multiple trip legs), carrying cash (or "traveler's checks" ) was always a dicey issue. Most of those employees used their own personal cards and submitted receipts for reimbursement. American Express stopped issuing traveler's checks although a few other banking institutions (Western Union and apparently CapitalOne) do still issue those, not all overseas places honor them or can convert them to cash.
This whole thing is nothing more than a dangerous and ruinous farce by a bunch of insane non-government people who have no idea what government does (and don't care), imposing nonsense on government because of this dangerous hallucination of some fictional "DEEP STATE".