Slate brought it up. Oval office decor is always a curiosity of the incoming Administration because they always put a personal spin on it.
Furthermore, as has been true since the days of Kennedy, optics matter. The Oval office is essentially a stage for Presidential optics, which is how the President looks to the American people. When actual work needs to be done, it's done in places like this.
For his part, Obama didn't like the Oval office as a stage, which is why it was rarely seen in addresses throughout his presidency. He prefered the East Room for speeches other President's would have given in the Oval office.