This kind of comment has been going on forever. Before mobile it was desktop apps, and it has always existed on the web where many designers prefer to work to some imaginary fixed size than make the most of the available screen. I feel like I've been fighting the same battle over and over since the 1980s. I even completely automated it for the Java ME world of smart and feature phones that existed before the iPhone and Android.
I can't resist saying this again, sorry. When the iOS SDK first came out I looked in vain for the API that returned screen dimensions. Checking the sample programs they all used literal hardcoded numbers, not even proper constants. I really was shocked, but apparently the powers that were had decided that 320x480 was what the masses wanted, now and forever.
And so Photoshop became the mobile UI prototyping tool of choice.
To understand why this is so wrong it helps to go back to the basics of art training. A good knowledge of anatomy - bone structure and musculature - is fundamental to being apply to paint, sketch, draw or sculpt people. Artists have to understand what's going on below the skin to make their work look good. The same is true for designers: prettiness is not everything, it's got to hang on the bones and move with the muscles.
At least this time round I'm not the only person wanting people to design adaptively. The responsive design and progressive development movements have understood that relative design and intelligent adaptive coding can not only address a few dozen pixels here and there but create optimal user experiences across widely varying screen resolutions.
The rest of you had better take heed and get with the program: there are more and more form factors coming to market. Making your pretty face fit the head it appears on isn't that difficult. Just get on with engineering it.