Directional antennas still obey the inverse square law, because the beam still diverges as it travels. So the amount of energy that you spend sending the signal gets spread over a larger and larger area, meaning that at any given
point in that beam, the signal is weaker and weaker, until it gets lost in the noise.
And even lasers diverge. An ideal laser has some minimal divergence that is inherent and cannot be overcome (if I understand correctly, it's because diffraction is non-zero even in vacuum). A true Bessel beam doesn't diverge - but it does not have a boundary, and hence requires infinite energy.