Why do some players play bizarre openings? I saw blitz games on the Internet (http://en.chessbase.com) between very high Elo rated players (above 2700) that played bizarre openings like: 1. a4 x 2. h4 xx 3. Ra3(or Rh3) xxx 4. Rae3 xxxx. The player who played like this still won. How to interpret these openings? Are these openings useful sometimes?

Here is one game: Player one 3084 - Player two 2983 0-1 3 minute game.

[Event "?"]
[Site "chessbase.com"]
[Result "0-1"]
[FEN ""]

1.a4 h5 2.Ra3 a5 3.h4 Ra6 4.Rhh3 Rhh6 5.Rhe3 Rhf6 6.Rad3 Rf4 7.Nc3 Rxh4 8.Nb5 Re6 9.Rg3 Rh1 10.Nf3 Re4 11.Ng5 Rxa4 12.e4 Ra1 13.e5 d6 14.e6 Bxe6 15.Nxe6 fxe6 16.Nd4 Qd7 17.Rb3 Qa4 18.Nxe6 Qc4 19.Nxg7+ Bxg7 20.d3 Qh4 21.Ke2 Bh6 22.Rxg8+ Kf7 23.g3 Qf6 24.Bxh6 Rxd1 25.Rf8+ Kg6 26.Rxf6+ exf6 0-1
The reason that top players generally avoid nonstandard openings is that they usually allow a sufficiently skilled opponent to equalize (with black) or gain an advantage (with white). 

To do this against an opening which you haven't seen before, though, takes time. In a blitz game, the opponent will not be able to figure out the best way to exploit an inaccuracy. A player like Nakamura (who probably played every single legal first move on ICC at some point) has enough middlegame and endgame skill that a slight opening disadvantage really doesn't mean anything.

Also, it's online blitz. They aren't playing for prizes, they aren't jeopardizing tournament invitations. They can basically do whatever they want and if they lose, nobody really cares. 

Edit now that you added the game:

Both players are clearly just messing around. Just because you CAN play chess well doesn't mean that you always want to. Don't try to draw conclusions based on this game.