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? 

that would be a big bloody waste of time. Unless you had a veriac, installed on each socket...*exspensive* youd have to switch your voltage and ampres by hand, every time you wanted something new. Or else wire in a whole lot of tranformers from the gitgo. any way you go, very exspensive, time consumeing, and bulky.