Table of Content (TOC) with numbers

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