You could also think of this as flipping a coin 30 times in a row and counting the different outcomes.
Pollsters know their results should look like this curve, so they don't have to talk to everyone. Instead, they randomly sample a smaller number of people and extrapolate using this curve.
This is also the curve teachers use when "grading on a curve".
And due to random errors, student test scores should follow this curve. If they don't, it might indicate cheating.
This is the Monte Carlo Method which was named after the famous casino on the French Riviera.
The Monte Carlo Method was first used on the nuclear bomb program at the Los Alamos National Laboratory.