Gas fraction distributions of AGN host galaxies (filled violin plots) and non-active galaxies (hatched violin plots) from cosmological simulations (EAGLE, TNG, and SIMBA in purple, red, and orange, respectively) and observations presented in this work (gray), scaled for α_CO = 3.6 M_⊙ (K km s⁻¹ pc²)⁻¹. The diamond markers give the mean value of each distribution. Gas fraction distributions from the observations correspond to the total gas fraction distributions built in Sect. 5.2. Galaxies in the simulations are filtered as in Fig. 9. The black arrow marks the leftward shift of observed distributions (black) for α_CO = 0.8 M_⊙ (K km s⁻¹ pc²)⁻¹.