Likely because neither one of them wanted to sacrifice big pieces of their future for a rental. Their window is just opening. They don't want to give up a long term piece for a win now piece. How good would you have felt giving up Anthony Rendon, Brian Goodwin, or Alex Meyer in 2012 for two and a half months of Machado?
Fair counterpoint, but I think the Phillies and Braves both have deeper farms than the Nats did then. We always had top line prospects like Rendon, Turner, Robles, and so on, but rarely did we have those types that would be B or C prospects, like an Alex Meyer. And is there reason to believe Machado wouldn't sign with the Phillies or Braves long term?
Full disclosure, I know very little about the intricacies of the Braves and Phillies systems nor do I know much about the Machado situation.