That is the idea...it is called balance, werewolves are deadly melee fighters and very fast as well strong and so they need weaknesses, transforming is one such vulnerability, lack of armor is the other and silver (at least in previous games) is as well.
I get why its like this, but I still dont like it. It wouldnt be unbalanced to take this out, but at the same time, I wont shed any tears, since it doesnt greatly effect me anyway. I only transform if I think I can without losing too much health while transforming, or if I have enough distance.