(I assume it's done that way to avoid inadvertent Siri launches. Just turned mine on, and it does require a motion as described, sort of like I'm looking at the screen, and then putting the phone to my ear as though answering a call.)
I have to admit I love the raise to speak feature with Siri. I've never had Siri on any devices before (my last iPhone was a base 4) but it is far and away better than the useless S-Voice I had on my Samsung. I use it all the time for setting calendar appointments and alarms.