Back in the mid-90s there was a huge push toward office furniture and home computer stands that had a pocket built in for the computer. Of course the dimensions were modelled after the mini-tower as it was pretty much an industry standard at the time. Now, suddenly, everyone's upgrading to ATX and the new cases wouldn't fit into the furniture... so, micro-atx to solve the problem.
I still have a lot of customers using that older furniture so I build quite a few uATX machines...
hmmmm....maybe I should look into selling office funiture...
--->It ain't better if it don't work<---