DCA-MCO was weight restricted a few days ago, which I've never seen on this route. I'm guessing it had to do with the weather; it was without a doubt a nasty stormy day in DC, Orlando and in between. Our flight path was unusually far to the East. We also had been slated for >40 minutes in the penalty box after pushing back but got an unexpected ATC clearance and only waited on the ground for 10 or so. I wouldn't have been surprised if we'd waited the full 40 or more minutes to have to divert for fuel.

Keep in mind that, especially with the shorter flights, you have to factor in the fuel weight al landing, not just take-off. So in the OP's case, it's possible that they did take on extra fuel to be prepared to dodge weather, and could have taken more, but would have been over landing weight if the flight path ended up being more direct.