It's a function vs style issue. There are clothes that I like the look of, but give me a big disadvantage by blocking more of my screen. With this option I won't see my cool outfit but others will. It will still give me a disadvantage by making me easier to be seen by others, but I can live with that.
If FGunz can implement an option to make my character always 50-75% transparent for me instead, that could work too