Moving from the consideration that matter fields must be treated in terms of their fundamental quantum counterparts, we show straightforward arguments, within the framework of ordinary quantum mechanics and quantum field theory, in order to convince readers that cosmological perturbations must be addressed in term of the semiclassical limit of the expectation value of the quantum fields. We first take into account cosmological perturbations originated by a quantum scalar field, and then extend our treatment in order to account for the expectation values of bilinears of Dirac fermion fields. The latter can indeed transform as scalar quantities under diffeomorphisms, as well as all the other bilinear Dirac fermion elements of the Clifford algebra. Phenomenological consequences follow, including the possibility of generating cross-correlation spectra from fermion perturbations. We then discuss how the macroscopic state for matter we propose can be interpreted as a non-Bunch-Davies vacuum, and then generalise this construction likening it to representation theory. Phenomenological consequences of this identification are then outlined.