Because if you wanna play with armor perks that benefits your play style, you'd be restricted. Due to affinity on armours, you can't mix and match guns, they do not have the same affinity match to your armor. Certain builds cannot benefit from the same affinity. Now, to be able to get the advantage of your perks, it limits you what you can play with unless you have 3 armor sets with 3 different affinity with the looks you want. Plus, you can't also use special perks on every armor like previously. Dreambane mode cannot be inserted to all.