You can’t get accuracy with a country of 300 million people by calling 900 or even 10,000. The sample is far too small. Its a fact that anything including weather can affect turnout and nobody knows who will win. Its also a fact that Trump still has far more enthusiasm than Hillary, and Hillary will have abysmal turnout except in precincts with ballot box stuffing.
If you dial up 10k registered voters in a single influential county in every county in a swing state you have a pretty accurate view of which way the state will go.
Accurate polling is important. Because accurate polling is good insurance against voter fraud.
One would think that with all the eagerness to pass federal statues that one would be passed where a Photo ID would have to be presented in order to vote.