I am quite sure that is done deliberately. I can't find a good resource to point to, but this article by Mark Boulton describes why you would do that with bulleted lists. I would assume that the same applies to ordered lists:

http://www.markboulton.co.uk/journal/comments/five-simple-st...

> With the advent of desktop publishing it became suddenly very easy and cost-effective to produce bodies of text. The problem was these bodies of text work within a box. Every character in this box had to be within the box, Hanging Punctuation requires characters to be out of the box. This was a problem for the software and as a result was ignored. An important aspect of typesetting just swept under the carpet like that. It’s a great shame.

And:

> A ranged left body of type is pretty much destroyed, aesthetically, when punctuation isn’t hung. The eye looks for straight lines everywhere, when type is indented in this way, it destroys the flow of text.