Tom Donaly wrote:

It's theoretically possible to make small, highly efficient antennas,
but since the radiation resistance of such antennas is low as well as
the loss resistance, the Q is high and the bandwidth stinks.
73,
Tom Donaly, KA6RUH

It also becomes difficult to transfer power to them without incurring
signficant loss in the matching network components.

Roy Lewallen, W7EL