# Why does logistic regression not have variance, but have deviance?

In this blog of Section 5.2, the author said:

For the linear regression, we evaluate the overall model fit by looking at the variance explained by all the predictors. For the logistic regression, we cannot calculate a variance. However, we can define and evaluate the deviance instead.

Why the logistic model cannot calculate the "variance"? The dependent variable has already been logit transformed, and becomes a continuous variable from $$-\infty$$ to $$\infty$$. Why does it different from the "regular linear regression", as is written is Section 2:

Different from the regular linear regression, no residual is used in the model.