One of the biggest turnoff in life is to be fat [and ugly]. But these days, people have to be politically correct. You will know it when members of the opposite gender ignore you when you speak and prefer to give their attention to the thinner and more attractive people around you.
you also need normal or ugly ones to play certain roles mah. if every actress has to be model standard and still has good acting skills, then it's very hard to find people to fill up positions.