[seabee]

But the home screen can be made symmetrical while maintaining the same distance between icons. So the question is why not do that?

Also as far as the outer margins are concerned, the badge extends the right side of the icon, so having the right margin wider was reasonable.

[sirn]

I think it is a lot clearer if you compared the margin using 3GS screen sizes:

    iPhone 3GS screen resolution (480x320)
    iOS4 17+19+19+19+18px
    iOS5 17+19+20+19+17px
    
    iPhone 4 screen resolution (960x640)
    iOS4 34+38+38+38+36px
    iOS5 34+38+40+38+34px

Before iOS5, they were trying to maintain consistent spacing between icons while in iOS5 they changed the home screen margin to be asymmetric while maintaining the same margin ratio between non-Retina and Retina displays. They can't use 35+38+38+38+35 because that would leave non-Retina at 17.5 pixels for left and right margin.

[pyrtsa]

It's not impossible to make it symmetric for both, though. With consistent spacings. E.g.

    19+18+18+18+19 (iPhone 3GS)
    38+36+36+36+38 (iPhone 4)

[sirn]

As I've said below[1], less margin on the edge will make more room for app title for the 2nd and 3rd icons.

[1]: http://news.ycombinator.com/item?id=3171496

[pyrtsa]

Oh true, missed that. Finally pulled out the phone to realize this. And then the other option 16+20+20+20+16 / 32+40+40+40+32 already has too big a difference between the margins on the edges compared to the ones between the icons. Makes perfect sense now.

[rkudeshi]

I suspect because they're trying to align to some type of grid.

(Even spacing between icons would require 39px of separation, and the odd numbering probably throws something off.)

[buddydvd]

You mean 37 pixels?

(640-(4*114))/5 = 36.8 pixels.

I wonder why they didn't choose this instead:

38+36+36+36+38

That would be most evenly spaced, symmetrical, and compatible with non-retina displays.

[sirn]

App titles. You can have less margin on the edge since you don't have to considers the app title length from the other side.

[buddydvd]

Ah, that makes perfect sense.

I guess, this would be pointless:

36+38+36+38+36 (18+19+18+19+18)

since the 2nd and 3rd icon wouldn't get the benefit of the extra spacing.

So the reasonable option would be: 34+38+40+38+34 (17+19+20+19+17)

[naz]

Right, on iPhone 4 it would be 39 pixels but on iPhone 3GS and lower it would be 19.5 pixels, which would require the icons to be aliased and blurry.

[gcb]

Uh? Just normalize 35 on the borders and keep 38 on icons.

What am I missing for this to be more complicated?