If the drain plug was reinstalled while everything was still warm or hot, and you tried to remove the drain plug while it was cold, it will be tougher to remove. If it was overtightened even a bit, it will be a LOT tougher to remove.
I follow a very exact routine every time I change my oil. Drive to the local autoshop, buy my oil and filter. Drive home, let the car sit for half an hour. Drain oil, replace filter, put in new oil. I have always been able to remove the old filter by hand, never had any trouble with the drain plug.
I did try doing an oil change when the car was cold once. Planned on doing it one morning, bought the stuff, got home, then had a priority interrupt. Next morning, drain plug was much tighter than usual, couldn't get the old filter off. Had to borrow one of those filter removal tools from a neighbor. First time I'd used one of those in nearly a decade.