The low-frequency Raman spectra of silica and lithium borate glasses in the frequency range 50-3000 GHz are analyzed. It is shown that the high frequency wing of the quasielastic excess scattering susceptibility has a significantly steeper slope than it is expected from any superposition of the Debye relaxations with different relaxation times. This rules out the possibility that the quasielastic Raman line arises due to the direct light scattering by relaxation centers. The predictions of the phonon-mediated quasielastic light scattering model are considered.