Because this team has absolutely no power. Our team slugging percentage is below .300, much lower than the next worst. Almost unbelievable to be this bereft of power.
When basically the entirety of the teams power comes from Freeman who's been struggling, it shouldn't be shocking. We no longer have Heyward or Justin, our next biggest power contributions come from either C or RF, where Markakis is way below average for the corner OF.
We're a seriously miserable team so far, as far into the season as we are, we have only 4 players with a positive fWAR, Markakis (off to another hot start), FLowers (who can't get more PT than Pierzinski) Castro, and Stubbs.
On some peripherals here's our rankings in all of baseball
BB%, 16th
K%, 19th
iso, 30th, by a lot (Astros have the next lowest iso and they're 48 points higher, meaning the team in 29th is closer to the top half of the league than the Braves are to 2nd to last)
BABIP, 13th
So looking at it, the failure is that we don't walk or strikeout well enough for the absense of power. When you have no power, you need to cut down on your Ks and put the ball in play. When you fail at those you can recover some value by walking a ton. We're not doing any of it well, and given that we have defensive issues at some positions, we can't afford to not be hitting.
In the end, the Braves are a team that is in a rebuilding mode that's truly painful to watch.