Electronics have gotten miniaturized, but that doesn't mean that a mechanical device that generates sound vibrations can be miniaturized. For example, an iPhone contains the computing power that used to take up a large room, but we don't have loudspeakers that are 0.01 inches in diameter and deliver the same sound output as conventional ones.
Antennas aren't mechanical devices; they don't need to transfer mechanical energy to air molecules. Also, their size is constrained by the power they need to emit as well as the wavelength of the signal, so we aren't going to see a cell phone antenna that's on the same scale as a transistor in an integrated circuit (tens of nanometers). An antenna that can only put out a microwatt of power won't be able to hit a cell tower that's a couple of miles away.
