Why do people say “so different” but do not say “so same”?

A popular definition of the word “different” as an adjective is dissimilar, differing, or not alike in quality or character.

A popular definition of the word “same” as an adjective is being identical though perhaps having different aspects or names.

I often hear sentences such as “Jane is so different than her twin Mary that you will never find them in the same shop.”

But I never hear sentences such as “Jane is so same as her twin Mary that you will always find them in the same shop on Saturday morning.”

This puzzles me, and I have yet to find a good explanation of why it is common to hear “so different” but it is rare — if not impossible — to hear “so same”.