As Darren said, they are named that way to support stickers. Also, regiments can change, become absorbed by other units, etc. For regiments, there is usually a "main" category to use if a person served in the unit during peacetime, and when there is a profile in need of the war category, they are created.
Yes, there is some chaos in the category system, but with hundreds of categories created/edited every day, we do the best we can to keep it at bay.