The "hey, so what" arguement....
If you reside in a open carry state & pack a sidearm or 2, then concealment may not be a legal issue. I for one, think a concealed firearm should be just that; CONCEALED.
For an armed professional(sworn LE, EP agent, PI, security, etc) it's just good tradecraft. I've seen a few cops, PIs & armed guards who had guns that printed.
It's unprofessional & shows a lack of skill.
For an armed citizen, a concealed weapon allows the element of surprise. A violent thug or group of thugs(which is more common in urban areas) may try a weapon grab too if you open carry.