When I left the DC area for good and moved back to Georgia in 2018, I had precisely the opposite experience. WMATA trains stopped running at midnight every night (including on weekends), which meant that any time I went anywhere I had to start looking at my watch at 11 PM and excuse myself early or else risk getting stranded. The chilling effect this had on social life was obvious. MARTA trains, by contrast, never stop running before 1 AM, and often I've been able to leave rather later than that and hop on a train. From the standpoint of public transportation alone, leaving the DC area was liberating.
True dat.
But that's because the DC metro system has been drastically cutting back their services because everyone uses Uber now.
My frame-of-reference, on the other hand, is the early 2010s, in which WMATA last trains on the weekends were 2:30/3:00am and were pretty packed even at those hours with the bridge-and-tunnel crowds.
And granted, I only spent a 3-day weekend in Georgia and this was a decade ago, but I'm also fairly certain it was 11pm "last call" for MARTA. That 1am you are citing must have been a recent development.