Why would brute strength be turned into a skill?
I'd argue that Might makes sense as a skill because...
* Some people can lift/bend/break things better than others
* Some people are naturally good at it
* You can get better at it with training and practice (both by building your muscles and by learning how best to apply your strength)
* No other skill covers the same trappings
* The ability (or lack thereof) to lift/bend/break things is at least sometimes of narrative importance in the kinds of stories the game is based on
To put it another way, if Might is not a valid skill, then you'd have to call Endurance, Discipline, and Conviction into question as well, at the very least. All four of those don't sound like something we'd call a 'skill' in common English, but they certainly work as "Skills" in the context of DFRPG.