Originally Posted by HSVTSO Dean

Well, for starters, if you're watching the TSO doing the wanding, that means you're not watching your stuff over on the x-ray belt~

Also, it has to do with the technique pattern and the screening of the head. It's far more easier done if your facing more or less straight ahead instead of having your head turned. It's never typically been a problem for me, except for a couple times when a guy turns his head suddenly as I'm wanding down the side of his head and he turns into the wand.

So, mostly, it seems to be a housekeeping thing.

The palms-up thing is supposedly so that you can't be palming something. Personally, I think that particular aspect of it is kinda' stupid. Having your hands more or less 'open' should be quite sufficient for that task, and even if I thought you were trying to palm something, it's not exactly a big imposition for me to tilt my head and glance under your hand.