As games become more and more important, referees are less and less inclined to blow the whistle. Obviously this helps the D, no need to explain there. I thought it was a NHL thing. NBA obviously too. Guess it's fundamental across pro sports, just a bit harder to spot in the NFL where playoff games are fewer. Obviously some refs are exceptions, but as a group pattern they pretty much fall in line. I would imagine, they don't want to be known as THAT guy who called the ticky tack and took it out of the players hands.