Is it coincidence or consistency of operation really matters for a smartphone brand?

The iphone 2G and the iphone 5S have the same exact button placement and configuration. The galaxy S1 and S4 have the same exact button placement and configuration. These 2 are the only really successful smartphone brands of the last 5 years. Everyone else on the other hand keeps fiddling with the button placement and/or configuration.

So what does this tell us? Is this merely coincidence that the only 2 successful brands have followed this consistency or does it actually attribute to their success?

People keep saying that samsung should get rid of the menu button but you gotta understand issues like these.