I've noticed it more as the airlines transition to the BYOD era. (The safety briefing overall.) In the last three years, I think I've been on two or three flights where I realized we weren't given the safety briefing.

The exit row briefing is a bit more important, as those folks will be the first responders when we need to get off the aircraft.

As a communication exercise, you are hoping that it penetrates through to enough people on-board that in the event of an emergency you reduce the level of panic. (Even by a little.) The people who didn't pay attention will most likely follow the crowd. The responsibility of the exit row folks is greater than other seats, simply because they have actions to carry out that effect the more than their own safety.