because your econometrics professor said so!

In statistics, the Gauss-Markov theorem states that in a linear regression model in which the errors have expectation zero and are uncorrelated and have equal variances, the best linear unbiased estimator (BLUE) of the coefficients is given by the ordinary least squares (OLS) estimator, provided it exists.

Carl Friedrich Gauss...

This theorem gives a relation between the total flux through any surface and net charge enclosed within the surface.

Gauss law states that the total flux passing through a body is 1 upon epsilon times the charge enclosed by the body.