I come across a practice where the logit (Intercept + beta* variables) is once again input as a independant variable in a single variable logistic regression against dependant variable to get intercept ($I$) and a beta ($B_0$). Finally, probability is calculated: $\frac{1}{1+e^{-(I+B_0\text{logit})}}$.
Why is this done -- since probability can be directly calculated from the logit in the first step?