Why isn't 3.e4 more popular in the QGA? According to the chess.com DB, 3.e4 is the third most popular reply in the Queen's Gambit Accepted - but why isn't it the most popular by a long shot? Isn't the entire point to remove black's central d-pawn so white can play a strong e2-e4? The moves 3.Nf3 and 3.e3 seem passive almost, but surely I am missing something. Maybe e2-e4 is taking up too much space too early, and you end up overextending yourself?
I'm not sure which database you are looking at: I see 3.e4 as the second, not third, most popular choice on chess.com, though not by much:



Here's what one author says about 3.Nf3:


  Throughout the history of the Queen’s Gambit Accepted, this has been
  White’s most popular move in this position. White does not hurry to
  win back the pawn that he has sacrificed. He calmly develops his
  pieces and offers his opponent as few targets for an immediate
  counterattack as possible.


Sterren, Paul Van der. FCO: Fundamental Chess Openings (Kindle Locations 1487-1489). Gambit Publications. Kindle Edition. 

and about 3.e4:


  For a long time this very natural reaction to 2... dxc4 suffered the
  same fate as 3 e3 and 3 Nc3: it was thought to be inaccurate because
  of 3... e5. The difference is that in this case White has the
  promising pawn sacrifice 4 Nf3! exd4 5 Bxc4!, when his development is
  swift and aggressive and Black will have to take great care in getting
  his king into safety. This is in fact a lively variation with chances
  for both sides.
  
  [...]
  
  Another standard device for counterattacking against the white centre
  consists in 3... c5.


Sterren, Paul Van der. FCO: Fundamental Chess Openings (Kindle Locations 1438-1441). Gambit Publications. Kindle Edition. 

My take is that it is not that 3.e4 is bad (it actually has better statistical results for White!), but it is a matter of taste and more people prefer to play more solidly.