Exactly, the SIM card stores almost no information compared to the memory components in a mobile device. A flash chip on on an iPod Touch stores 64GB! The SIM is a hangover from the old days that the cellphone industry should shake off. But of course, an electronic SIM would mean a single phone could be dynamically made to shift carriers, and the carriers wouldn't like that would they? In my opinion it shouldn't even exist.
Next best thing? Tiny SIM.