Why are protostars not graphed on the hr diagram?

Protostars are not plotted on the Hertzsprung-Russell (H-R) diagram because they are in the early stages of stellar formation and do not yet achieve hydrostatic equilibrium. During this phase, they are still accumulating mass from their surrounding material and have not yet reached a stable temperature and luminosity. The H-R diagram typically represents main sequence stars and those in later evolutionary stages, where their properties are well defined and stable. Thus, protostars are not included in this framework.