They and/or their coaches don't want to commit to actually trying for it. You'll see the batters half-heartedly start to bring the bat up for a bunt occasionally, but that's not going to actually net you a bunt even if you get a good pitch to bunt. And the fielders are too smart to fall for these little bunt feints, because they know the Astros don't actually bunt a lot.
We need video and then a gif of that play as soon as possible. It transcends baseball in its usefulness to describe situations.