  The origin of obscuration in Active Galactic Nuclei (AGN) is still an open
debate. In particular, it is unclear what drives the relative contributions to
the line-of-sight column densities from galaxy-scale and torus-linked
obscuration. The latter source is expected to play a significant role in
Unification Models, while the former is thought to be relevant in both
Unification and Evolutionary Models. In this work, we make use of a combination
of cosmological semi-analytic models and semi-empirical prescriptions for the
properties of galaxies and AGN, to study AGN obscuration. We consider a
detailed object-by-object modelling of AGN evolution, including different AGN
light curves (LCs), gas density profiles, and also AGN feedback-induced gas
cavities. Irrespective of our assumptions on specific AGN LC or galaxy gas
fractions, we find that, on the strict assumption of an exponential profile for
the gas component, galaxy-scale obscuration alone can hardly reproduce the
fraction of $\log (N_{\rm H}/$cm$^{-2}) \geq 24$ sources at least at
$z\lesssim3$. This requires an additional torus component with a thickness that
decreases with luminosity to match the data. The torus should be present in all
evolutionary stages of a visible AGN to be effective, although galaxy-scale gas
obscuration may be sufficient to reproduce the obscured fraction with $22<\log
(N_{\rm H}/$cm$^{-2})<24$ (Compton-thin, CTN) if we assume extremely compact
gas disc components. The claimed drop of CTN fractions with increasing
luminosity does not appear to be a consequence of AGN feedback, but rather of
gas reservoirs becoming more compact with decreasing stellar mass.
