I think this argument of liking combat speed faster or normal is very much to personal taste and mood.
For me personally I would welcome the option to adjust combat speed.
Sometimes, depending on my mood, I feel like speeding things up, while other times when I'm more relaxed and immersed, I want things to flow at normal speed.
It's almost impossible to argue they should not add it, because it doesn't hurt anything, it simply enhance the game by giving the player more options.
