Because the big cities are Democrats and they wait to cheat — just as much as is required.
I have often wondered what would happen if we had an election wherein our people out in the suburbs and country would withhold reporting their totals until the urban areas reported, just for the h*ll of it. They could say things like, well, we had to take the time to gather all the data and check it from all those far-flung precincts, took a lot of time, blah blah blah. How would the ‘Rats react to that? Would they send their goons out to demand the totals?