Why It Matters That McMaster Isn’t Taking Off The Uniform

I can see a few reasons for this.
1. He's a career Army officer.
2. The oath he took states that he "will support and defend the Constitution of the United States". Wearing the uniform reinforces that oath, especially when he's surrounded by the political types in the NSC.
3. If he was to wear civilian attire, as he is authorized, people might think he's more interested in blending in with the current WH philosophy.
4. He still has to work with the rest of the military leadership, as well as other more senior officers. It shows those officers that he's not a political animal.

There's probably more reasons I could think of, but that's it for now.

It will be interesting for sure. Because he's staying in uniform, I expect he'll watch his p&qs and not make a fool of himself like the last guy appointed the position.

Here he is way before this position. This man and his Tank Battalion made history!
https://www.youtube.com/watch?v=qX1cvcHjKu4