AKA is used specifically in the FTM software to allow additions to the index of names.
Firstly, it can be added as an extra entry in the index - FTM normally only adds the preferred name to the index. (For this reason it might require a surname).
Secondly, it can be included in the preferred name for display purposes or index purposes e.g. John "Johnno" Smith.
Using the NAME fact for this purpose would not work as which one would you choose?
Those people who use AKA for married name do it in order to get the name to appear in the index under both possible surnames. I don't personally use it this way, but it is an interesting idea.
If you want to do away with AKA then you need an "Indexed" property added to the name fact to indicate that it should appear in the index, and you need a NICKNAME fact to display the name in quotes between the normal name and surname. AKA fulfils both of these possibilities - albeit not both at the same time.
Just because you don't use the AKA fact doesn't mean it shouldn't exist.