So much low scoring, why so?

Right after the playoff seeds had been set, I made a post trying to predict both the results and the aggregate scores of each of the two-legged series. So far not only have I been wrong in regard to who the winners of the series will be - assuming that both FC Dallas and the Los Angeles Galaxy manage to hold onto their leads against Real Salt Lake and the Seattle Sounders respectively - but also the number of goals that were going to be scored.

My prediction was about 6.5 goals per two-legged series in total aggregate. So far, the remaining four games will need to be pretty damn high scoring if they're going to hit that mark. Three games ending 1-0 as well as a 2-1 win by FC Dallas have given them a 1.5 total score between all the games and something makes me doubt that there will be four games now with 5 goals a-piece.

Is it goalkeeping that's keeping the scores so low in this early age of the playoffs? I don't think so. Despite a couple of highlight saves so far by names like Donovan Ricketts, Matt Pickens etc. most keepers haven't had much to work with. In fact, I'd make the argument that some of the best goalkeeping all playoffs so far has been from Kevin Hartman and Nick Rimando in the 2-1 'high scoring' affair between Dallas and Salt Lake.

Any theories out there for why it's been so torrid? Bad finishing? Stifling defense playoffs-wide?