Most likely because an engineer designs it, or it's designed by committee. Let's see, how can we sell this same microwave that cost us $30 to make, for twice the money? Oh let's add "features" such as a 'popcorn button' that makes popcorn, or a 'defrost tbone steak' that perfectly defrosts...
etc etc, That said, the inverter technology in the panasonics are worth paying for... not to mention that they do have tactile buttons and a knob... http://www.cnet.com/pictures/panasonics-nn-sd997s-microwave-...