Mass versus luminosity diagram of the 151 protostellar cores discovered, with detectable luminosity, in the ALMA-IMF massive protoclusters (color-filled squares, green, orange, and red for Young, Intermediate, and Evolved protoclusters) compared to reference studies of low-mass protostars (pink circles), IR-quiet high-mass protostars (cyan circles), and clumps hosting UCH II regions (red circles). The surface density of observed protostellar cores is to be compared to that predicted by a parameterized model (gray scale image), here with decreasing accretion rates and intermittent accretion (Duarte-Cabral et al. 2013). The final stellar mass of a protostar is predicted by the evolutionary tracks, for 0.08–50 M_⊙ core masses, associated to this model (white curves). The yellow curve theoretically separates high-mass protostars from sources developing an H II region. Current scenario, assuming an accretion from a gas reservoir decreasing with time, does not fit the protostellar number density observed for ALMA-IMF protoclusters: protostellar cores more massive than 2 M_⊙ are clustered in areas where the normalized surface density is predicted to be very low (~3 × 10⁻⁵), while only a few of these protostellar cores are found in areas where the surface density is 30 times higher.