The power needs conversion somewhere and no one has designed a "cord" that contains the needed circuitry that small.
Now there were laptops that put the power brick inside the laptop but as you imagine the laptop weight and heat increased.
I have a HP tx1219 and have had a couple of power supplies go bad, it seems to be at the plug thing that goes into the laptop. What I want to know is are there power supplies available without the big block/brick thing. If Im going to buy another power supply I'd like to get one without the block/brick if they are available.