Downloadable Sounds?

So I know you can get new sounds for a keyboard by running it through your computer and some program, but is there a keyboard out there that can get new sounds actually on the keyboard (plug it into the computer, and download the sounds onto the actual instrument itself)? It seems like it would be a pretty easy thing to do with how technology is these days, but I haven't found one yet. Just curious

There WERE such hardware synths around a long time ago, but that era has passed.
Soft virtual instruments are the current IN thing.
The thinking was that a good hardware synth had to have all the computing power, memory, storage and monitor screen of a PC, so why package a whole special single purpose computer in a box ?
Easier to sell just the software as add-in to "everyone's" existing home computers - yes ?