There is nothing in the singing preventing them from playing it. Bono may have said that, but he's the politician for the band...that's just another way of him saying "I know you guys want to hear it, but we - as a democracy - don't feel like playing it".
Others are correct, they were going to open ZooTv with it (segue into ZooStation) and scrapped the idea when the arrangement didn't work. They put it on the shelf -essentially permanently - because Edge couldn't remember how he played it and it was in a
fast 3/4 (I think Breathe is much slower). Edge is using a particular slide-style (maybe even a literal slide) with an odd chord structure for the big 'riff'. I am guessing that is what he can't remember. I've written songs myself that I can't remember how I played. Sometimes you just try shit...
That said, they could play it, easily, if they really wanted to. But let's face it, it is only a bone to throw to hardcore fans. And they've become, increasingly, more of a 'greatest hits' band. But shit, if they can break out Zooropa, they can do Acrobat.
So the answer to the question is, regardless of what Boner or anyone else is saying, they (collectively) have had no recent desire to go back and rehearse it.
My motto is to blame Larry first and ask questions later.