iPod / iPhone / iPad /三星底部正面上的按鈕是出色的UX。為什麼其他移動設備製造商也不在前面提供這樣的按鈕？大多數智能手機的側面都有硬件按鈕，而背面有一些硬件按鈕（！）。在大多數情況下，手機都放在桌子（或其他平坦的表面）上，所以將硬件按鈕放在前面不是更有意義嗎？
Well first the button on the front of the iPhone isn't the power button, they place theirs on the side as well. The reason for not putting the power button on the front is that where the users can most easily reach, so that real estate is used for functions that occur more commonly like backward navigation such as the iPhone.
Also many other phone manufacturers do have button on the front bottom panel that serve roughly the same purpose:
With regards to buttons on that back:
Therefore it is arguably just as easy to use if not easier than other button placements:
LG said the change in location, odd as it may seem, was actually much more comfortable and intuitive for users.
The real benefit then comes in the form of screen real estate. By moving all buttons off the side and face of the phone you can use that extra space to maximize screen size:
By moving the buttons off the handset's edges, Woo added, it enabled LG to design phones with ultrathin bezels. The G2's bezel, for example, measures just 2.65 mm, and the G3's is even smaller at 1.15mm. And when it comes to screen real estate, smartphone users know that bigger is indeed better.
Sure this is just one case but I think it is likely that attempts at easier finger placement is the reasoning behind most mobile device button placement.
EDIT: Also note Android OS phones have these "buttons" displayed on the screen allowing them more flexibility in hardware button location: