Maybe I incorrectly assumed that workers with a few days off might be online doing a little shopping in their spare time
My sister is affected by the shutdown (she works for NASA) and I can tell you that shopping is as far from her mind as possible today. She has no idea how long this will last and if she will be paid for the time she is furloughed. She has a mortgage and other bills to pay and has to make her emergency fund last through this. I imagine many other of the laid off federal workers are in the same boat. Many likely do not have an emergency fund like my sister did, so their situation may likely be even more dire.
Then there is the military... I am a member of a military family (reserves) and while they are still getting paid, any unnecessary drills have been canceled. That means the couple hundred bucks that reserve families normally would be getting (and likely use for extra spending money) is gone this month.
Not to mention that military contractors are on a case by case basis on whether they will be paid.
Then, let's see, how about all those restaurants and shops near federal facilities. They rely on federal workers to eat and shop. And tourism areas, no tourists will be going to National Parks so no tourism dollars will be coming in for those areas.
These are just a few of the examples of how the shutdown ripples past just federal workers and affects the incomes of those not in the federal government.
The shutdown did coincide with a new quarter, but likely many marketers have also realized that the shutdown could affect a large portion of the population, so may be holding back. After all, they could just up spending later when the shutdown is over.