Hello!
Although many people look forward to Black Friday because of the sales and discounts being put on everything, many other people are too. This ends up causing many lines in front of stores and within, waits accumulating up to hours, just for a couple items that might have a 50% discount. I don't exactly know about you or another others reading this answer, but with these couple hours, I can do a lot of other stuff that might not just be waiting in line. Some might even consider it a waste of time between waiting in line in the cold and waiting some more inside of the store.
Also because of the amount of discounts being placed, items in stock can run out extremely quickly, meaning that by the time you actually get into the store, the item you wanted could have already been out of stock, meaning that you waited all that time for practically nothing.
Hope this helps!