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 mean that’s possible but whould they even need to? If one company had a “Christmas sale” and other had a “boxing week blowout” will folks even care, or will they just go to what place has the better deals?
This is the corporate version of the prisoner’s delima.
And no, corporations would absolutely try to fuck over their competitors.