Probably because most hunters don't have it and therefore don't really care.
I'll care a lot more about sims featuring the mantle if I ever get it, but chances are I won't, since it's just 1 of 7 BM spec legendaries I don't have yet, and it seems that I'm getting another legendary approximately every 2 months, it's greater than 50% chance I still won't have it 6 months from now, and there's bound to be patches in that time that will change all the sims anyway.