The Nats game was rained out last night; it happens. Fans can exchange their unused tickets for tickets to a future game; as is standard. Unfortunately, that "future game" is very specifically Thursday afternoon's game, no substitutions.
The Washington Post notes a whole bunch of fans who are royally pissed that they have to go to Thursday's makeup game at 4:05 EDT, because, you know, its during the workday. It didn't used to be like this! Until this season, the Nationals gave fans the option of exchanging their rain checks for tickets to any future game, as long as identically priced seats were available. That's still the policy of the majority of teams with published policies.
So, why the change? The Nats put out the briefest of statements:
“Due to higher demand and less capacity, we’ve had to modify our ticket policy.”
Basically, they'd rather sell warm-weather tickets than give them away, and it's damn hard to fill up the ballpark for an unscheduled Thursday afternoon game. On the heels of Washington's unpopular decision not to refund service charges on tickets for playoff games that were never played, it's not a great look.