Why better theoretical models are needed to understand nuclear medium effect in the DIS region?

In the case of lepton scattering processes induced by charged leptons and (anti)neutrino on nucleons and nuclei, the inclusive cross sections at low energies are expressed in terms of structure functions corresponding to excitations of various resonances like Δ, N*, etc., lying in the first or higher resonance region depending on the center of mass (CM) energy W of the final hadrons. On the other hand, at high energies and Q², the inclusive cross sections are expressed in terms of the structure functions corresponding to the Deep Inelastic Scattering (DIS) processes. The DIS region is understood to be the kinematic region with the center of mass energy W ≥ 2.0 GeV and Q² ≥ 1.0 GeV²