Switching to the quarter system (instead of halves) and a huge increase in talent have both increased the quality of play and the free-flowing game.
In 2003, only one team (out of 14) scored over 73.5 points per game (Detroit Shock, 75.1 ppg). Nine teams averaged in the 60s for ppg and 12 out of 14 averaged less than 70.3 ppg.
In 2006, 9 out of 14 teams averaged at least 74 ppg, with two teams in the 80s, five teams over 75 ppg, and only teams at less than 71.5 ppg.
In 2011, 7 out of 12 teams averaged at least 77 ppg. Four teams averaged more than 80 ppg, and only three teams averaged less than 74 ppg.
In 2016, to date, 6 out of 12 teams average at least 84 ppg. 9 out of 12 average at least 80 ppg. 11 out of 12 average at least 77 ppg.
And it is not a foul fest that is contributing to the increased scoring. Here are the league averages for total free throw attempts per team by season, with the league average for free throw percentage:
2003: 625 (74.3 percent)
2006: 698 (74.8 percent)
2011: 641 (77.0 percent)
2015: 631 (79.5 percent)
Free throw attempts are actually down from ten years ago, while scoring is up. But free throw makes are significantly higher (I used 2015, as the last full season for a more accurate comparison).