What's the point of 1.g3?

I'm struggling to see why anyone would play this. If you like the King's Indian Attack, then 1.Nf3 preventing 1...e5 seems much more logical, while both 1.Nf3 and 1.c4 are more effective ways of reaching the Catalan Opening than 1.g3. So, why play this move then?

Also 1.e4 e5 2.Nc3 Nf6 3.g3 is another possibility which seems stronger than the immediate 1.g3

I'm neither playing 1.g3 (actually I'm a 1.Nf3 player), but I'd say that 1. g3 doesn't exclude some Ne2 systems of the English. Also, it might be actually a provocation of 1. ...e5, so that after 2. c4 you are in Reversed Sicilian territory (probably :)).

The point of 1 g3 is to play 2 Bg2.
As opposed to 1 Nf3 it keeps options open to play Ne2, Nh3, or f4. Most often you will play the natural Nf3 anyway.
1 g3 sort of provokes 1...e5. If you play 1 e4 g6 and black, you are happy to play 1 g3 e5 as white. You can also play 1 g3 and 2 f4 for a reverse Leningrad.

@tpr, right.

@soni777, don’t think about cashing in too early. Furthermore,

-flexibility is paramount
-fianchettoed bishops are very important in modern chess, they yield a latent and sustainable dynamic potential

The players that developed these flank openings...Were known as the "Hyper- Moderns" They changed the stogy accepted openings of the Steinitz and Tarrasch era. Management of the fianchettoed king bishop is paramount to the success or failure of the various flank openings. Their efforts gave us the game as we know it today by expanding acceptable opening play. :]

Can't always go "1 g3 and 2 f4 for a reverse Leningrad" :P

1. g3 e5 2. f4 exf4 3. gxf4 Qh4#

Besides all that was (well) said, 1. g3 has the point of getting the other player thinking on "what's the point of 1. g3".