Table of Content (TOC) with numbers

The Table of Content at Wikipedia use numbers for an ordered list.

But the headline doens't start with this number.
Why?
It look wrongs for me, maybe because I'm used to the same result as in books with chapters.
I think a number in the headline (1. History) looks like a ordered list with steps that must be followed in order like a cook recipe. But without a dot like "1 History" doesn't look right.
Is there a UX best practice to use numbering in a headline like a chapter with an index (TOC)?