The grid based icon system isn't an innvoation, nor is it even a significant part of the iPhone product -- but it's a key part of the trade dress, which explain

The grid based icon system isn't an innvoation, nor is it even a significant part of the iPhone product -- but it's a key part of the trade dress, which explains why Samsung were so keen to appropriate it. It allowed them to market their phone as seemingly substantially similar to the iPhone. It allowed Samsung to imply "this product is basically the same as that iPhone that everyone's raving about". Customers didn't need to think they were buying an Apple product to be misled.