Is this prevented by physics or cost or just no one has the motivation?
Handheld CB radios do exist and are cheap, but I've never really used them.
I have personally made voice (single-sideband or SSB, which is analog like AM without wasting energy transmitting a carrier or redundant sideband) contacts with a 5 watt portable (Elecraft KX2) between countries in Europe, using a meter-long whip antenna and a trailing counterpoise wire.
These radios are incredibly complex weak-signal equipment, and that is reflected in the price.
That said, it is fun. Using morse code to do the same is even more fun.
I would never rely on this for off-the-grid communication, though.