What Does a Dozen Do?

A dozen does fine as a number of eggs
or of cupcakes, or doughnuts.

Roses often come in dozens.
Tribes and disciples too.

Some dozens are dirty,
and others are cheap
(selling for as little as a dime).

Bakers can't seem to count them properly.

There are a dozen months in a year
and two dozen hours in a day.

A dozen drummers drumming
makes for a happy song,
but a dozen dozens can be gross.

A dozen does very well
in the duodecimal system.

With all these wondrous things a dozen does,
I wonder what a dozen doesn't?