Because by definition the correlation coefficient is independent of change of origin and scale. As such standardization will not alter the value of correlation.

How does standardizing variables affect correlation coefficient?

Calculate the correlation coefficient, r, for your standardized variables. Multiply the individual standardized values of variables x and y to obtain the products. ... The higher the value of r, the stronger the correlation is between the two variables. A correlation coefficient of zero indicates no correlation.

What happens when you standardize a variable?

Standardizing makes it easier to compare scores, even if those scores were measured on different scales. It also makes it easier to read results from regression analysis and ensures that all variables contribute to a scale when added together.