Why does the removal of religion sudden transform an event into a commercial event. And how does removing the religion make it commercial, but not having it in

Why does the removal of religion sudden transform an event into a commercial event. And how does removing the religion make it commercial, but not having it in the first place does not (Thanksgiving/Independence), I do not get that seemingly popular opinion. I am not religious, though I was raised in a somewhat religious family, and Christmas has always been a good family holiday. Don't need to have a belief in a benevolent God or his son to enjoy it or to celebrate Christmas. Plus, I'm sure that even if everyone was a devout Christian, businesses would still be marketing for Christmas sales.