For those with vision impairments such as color deficiencies, low vision, tunnel vision and difficulty seeing rapidly moving information, the ability to organize the UI to the end users’ preference helps to mitigate problems with seeing important information at a glance.
Additionally, the ability to change the colors, size and position of various elements on the UI help those who cannot differentiate between certain colors. While those with other eyesight issues can independently arrange elements to benefit their style of gameplay without needing to petition the developers for a set up that would work for them individually.
Giving multiple alternatives helps alleviate the need to add multiple schemes further down the road in the development cycle.
The most preferred method for dealing with customizing the graphical user interface is to allow the user to individually define how they would like the elements to be arranged.
Understandably, this is an expensive endeavor. However, it may be an additional argument for iterative interfaces that can lead to smoother development processes and better overall design. Currently, consoles rarely allow the user to change the position of UI elements. It is far more common in PC. But in those circumstances, gamers that have a difficult time seeing certain positions on screen benefit greatly from those games that do allow custom interfaces.
A woman with macular degeneration has difficulty adjusting her sight quickly to various points on the screen. If she is able to redesign the UI so that the elements of most importance are within her visual range, the time spent in that game will be dramatically less frustrating.