That's been going on since the inception of conventions. there's a great story on how Lincoln was nominated by the party bosses.
The rise of media has meant the decline of importance of conventions as candidates are selected by the popular vote through the media and not by by convention deals. The saying is that Lincoln would not have won nomination in today's politics but Clinton never would have been nominated by party bosses in convention.
So you may not get the 'message' that's imparted when party activists and the base refuse to vote.
The message remains the same. Those who stay home don't care or maybe are sulking with a "take my ball and go home" attitude.
Those who actually care and are responsible - if alienated - will go out and vote for another candidate. That's a message sent by someone who cares about the nation - not someone who stays home.