I think Ed is spot on, as usual. Today's "rider" is looking for an experience that they don't have to control. Hitting a road obstacle will produce head motion and bar reaction...and most of the time that reaction will modulate within a few cycles to zero. If you want a damper to "crank up" so you have no reaction, then you will limit your ability to move the bike with agility.
True "head shake" is brought about by steering inputs made by poor tire condition and poor suspension setup more than anything else. Or, it can be faulty design such as the Harley Death Wobble that existed on some of their big framed bikes prior to 2009 when a frame redesign corrected the issue.
I don't ride in a place where speeds on the street can approach "race speeds and I feel steering dampers on well sorted bikes, like MV Agustas, are not required on the street.
I have a B3 800RR, a B4 1090RR and a F4 312R....all of them came with steering dampers and all of those dampers are backed off to minimum so as not to interfere with my steering inputs.
At no time have I felt the need to crank 'em up due to head shake.
Now, if you are one of those "I need to wheelie and ride like a maniac on the street" types, then by all means, install a damper so your front wheel lands straight and you don't kill my family.