AC adapter size

Why do AC adapters have to be so big?  Can't they be designed more compact to say, 1/4 their size, or about the size of a regular outlet but with more height/depth rather than socket stealing width? 

AC adapters typicaly use a step down transoformer, followed by a bridge rectifier and a big capacitor. The weight comes from the honking block of iron wrapped in yard upon yard of copper wire transformer. There are less noisy, lighter weight, smaller adapters that don't use a typical transformer. These also usually run upwards of $50 for a cheap one. And they still can get in the way because you have a high voltage circuit attached to wall outlet prongs. The real solution of course is to put the adapter somewhere a couple feet down the cord from the plug. But this too can get annoying.