Re: is shorter excuse
<span class="small" usage should be an EXCEPTION to the base <Body>, <P>, <Div> style, not frequently appear.
Since it is a limited (in frequency) use, the few characters
saved 
is a big waste of effort on all but the (ridiculously) HUGEST book
IIRC there are a few special cases where a nested <span> worked around a device flaw. Again, those are exceptions