Why no moisturiser? Isn't this essential for our skin?

Why no moisturiser? Isn't this essential for our skin?

I always thought moisturizer was important, but the derm told me otherwise. He said that the moisturizer was not allowing my skin to dry out properly and therefore making a better environment for the acne bacteria. I think my skin is getting used to not moisturizing now.

I wanted to follow his routine exactly so he can figure out what works for me and what doesn't. It's only been 2 week since I'm doing this, so I think it's too early to tell if it will be a permanent solution. I am slowly seeing improvements though.