This means no sales, no themed merchandise, no decorations. December 25 and most other day are treated just like any other day for all stores malls, restaurants, ect.
You’d still get non religious holiday events like mothers days, or independence days.
What whould change?
I’ve noticed that seems to be happening, especially with companies like Amazon, whom I work for, aside from the money they can make from it. That said, we also have an example of that in the form of old Soviet Russia. They had actually eliminated most holidays.