First, start with they're horrible bunters. That's probably a gimme. If you watched any of the CWS, you'd know a lot of players you'd think could bunt can't. And you know college coaches make them practice it.
Second, the pitchers are pitching into the shift not away from it. So now you have a bad bunter trying to bunt a pitch(inner third) that's difficult to bunt the other way.
Third, the batter can't give away the bunt or the pitcher/defense can react. Now you have a bad bunter trying to bunt a pitch that's difficult to bunt the other way at the very last moment. It's a recipe for failure.
Finally, you can't compare bunting against a Major League pitcher to your Little League or slow pitch softball experience. It's not comparable. LL pitchers are just trying to get it somewhere near the plate and SPS pitchers are throwing it underhanded at 23 MPH.
And, as for Chris Davis swinging away in a 1 run game, are you really suggesting he should be bunting? I've heard he hits a few homers and, with one swing, he ties the game. If he bunts for a single, he'll need a couple more hits to score. So, essentially, the O's have to hit at least .500 for the rest of the inning. How many teams have a .500 average?