Because it's terrible.
The Grob's Attack, and Why We Don't Play it More???

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I have started to play ... the Grob's Attack. I don't understand why we don't play it more
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Because it is junk.
That some IMs beat amateurs with it means nothing.
Why start the game by giving yourself a handicap equivalent to 200 rating points or more? But if you insist on playing it then go ahead. Waste the time in which you could be learning openings that will serve you for the rest of your life.
MIke Basman might have become a GM if he had spent less of his time on rubbish openings (1. g4 for white, 1. ... a6 for Black).

Mr. IM pfren, "white is just worse". Any engine will say white is "just worse" after the first move. The point is not to prove the Grob is a perfect opening. The point is to show that black had better know how to respond or black will be in big trouble...which is the case with all openings.
pfren is (as usual) right. There is no need for Black to "know how to respond" to junk moves whether they are played on move 100 or move one (1.g4) , except perhaps in Bullet. If you have time to think then you just work out why it is so awful and play good chess to exploit its deficiencies.

The thing about 1.g4 d5 is that although it's theoretically better for Black he does need to play actively and accurately constantly or else he'll just get destroyed on the light squares. One or two passive moves from Black (which is frankly expected from class players) and White is doing more than fine.
I remember seeing Timur Gareev play this in blindfold blitz once against an IM. The IM played a really bad passive move and was utterly decimated. If it can happen to him it can happen to anyone.
1.g4 e5 is just depressing though.

blitz used to prove the practicality of an opening? JOKE.
Do we really need 6 hours to prove that 1.g4 is a bad move?

blitz used to prove the practicality of an opening? JOKE.
Do we really need 6 hours to prove that 1.g4 is a bad move?
Only took me 30 seconds.

One of the best reasons to learn Grob is to learn how to defend it. It's full of traps, and if an opponent hasn't seen it, he or she is open to make mistakes. This goes past the opening and leads into the mid game, when the strange pawn structure continues to confuse the opponent. From my experience, it causes both players to castle on the queen side. If black over pursues in the mid game, he or she is open to a surprise loss or combination. I've actually played a few games when I castled on the queen side and then brought the king all the way across the board during the midgame to assist in a surprise combination for the win. If you haven't tried it yet, I would recommend it. It's nothing worth mastering, but it's certainly worth trying.

I couldn't agree more with ejsmith - don't knock the Grob til you've tried it a few times, but do just a bit of research as well before using it. Because he is right about the potential traps. Play your cards right and you will pick up more opposition Queen's rooks than you can shake a stick at, plus completely paralyze Black's K-side knight early in the game. However, play your cards wrong and the same or worse fate will await you in the jaws of the mighty Grob.

Indeed. I love the Grob. I don't play it as much as I used to, but I have always coveted it's straightforwardness. Heh. Blitz, to me, is the best time to wheel this out. Just like the BDG, experienced practitioners can rack up some points.
It has some practical value. Not unlike the St. George or the 1. h3, black will either overdressed or play too passive. OTB is cool too. Online not soo much because of engines usage.
But overall, I am highly recommending studying this. No doubt.
When I play Grob as black I let white win the QR after 1.g4 ..d5 2.Bg2 ..Bxg4 3.c4, ..dxc4 Losing the exchange is worth it! You have much more fun and many ways to attack. White is gloating because he thinks he tricked you but when he realizes he has nothing but disorganization, it breaks his heart.

Hello Chess Fans,
I am about to get the book "Play 1.b4" by Yury Shulman and Nick Conticello. But until then, I have started to play the exact opposite, the Grob's Attack. I don't understand why we don't play it more, because it gives White some great attacking opportunities. Here are two of my recent games. Any comments???
Here is the other one...
Thanks for reading. I would appreciate any notes or analysis you have.
Brilliant, mind boggling games. You either study or have talent to rival or even dwarf the worlds elite. Woaaaah.
Brother, the man has not been on the site since 2013 lol.

It is probably fine OTB if your oppoent does not know you play it.
Will likely put your opponent in time troube by the time make middlegame
It one of those openings where you only find out how to beat it, once you go home after the match having been swindled in an unfamiliar position, despite being theoretically fine

There was a player here in Indiana who played this often, in the Indiana State Championships even. I think it's a garbage opening, but here is the thing. If you play with just about any opening long enough, work out the obvious replies, then you can win a lot of your games with a crap opening just because most people will be surprised and had not prepared against it.
And make sure you don't play bullet & blitz.