Not really quickly, but has been increasingly happening over several years. Coaches are holding guys out of duals for selfish reason, which I understand to an extent as a former coach.
However: for the sport to survive and thrive, a lot of these guys should make the long trip, the extra weight cut or wrestle with an ouchie or two. I would hazard a guess that many of our better publicized "ducks" are guys that would be playing in an NCAA football game on Saturday if they had the same booboo or case of sniffles. There's just no tangible incentive to do so right now.
Thus we are increasingly headed to a land where duals matter less and less and all that matters is one weekend in March.