I understand that you don't get reputation in Meta as it's a part of AskDifferent, and meta.stackoverflow is a bigger "independent" site which does.
But why doesn't it show badges from main site here?
Badges on Meta mean different things — for example, the answer badges on Meta means that you've answered a question regarding how the site functions, not the site itself. This is substantially different due to the difference in subject matter.
As an aside, reputation is tracked independently on Meta, just not shown.
My view is that the badges do depend on the meta or non meta site so can be split up - the rep does not give any extra privileges to the meta site so there is no point in a separate reputation here.
I would note that meta.stackoverflow is getting changed so that there will be a site for StackOverflow and an overall site for all Stackexchange sites