The NFL instituted a new rule that was designed to encourage teams to accept touchbacks instead of attempt returns, but it already appears to not be working as designed. They thought that moving the touchback out to the 25 instead of the 20 would create less returns, but teams are strategically kicking shorter because of the new rule.
That means that the ball isn't getting into the end-zone in order for teams to accept touchbacks more, which will actually create more returns instead of less of them. Teams figured out that they could pooch kick their kickoffs short and high, thus creating a better chance of stopping return men short of the 25 yard line.