Why are stars more tightly packed near the centres of most globular clusters?

Stars are more tightly packed near the centres of most globular clusters because these systems possess stellar distributions that resemble isothermal gas spheres.12

The concentration of stars in these regions is determined by the complex dynamics of the cluster, which can be modeled by accounting for the orbits of individual stars, frequent encounters between member stars, and the influence of external forces, such as the tidal effects of the Galaxy. Astronomers use specific dynamical models to describe this structure, often utilizing the "core radius" to measure the degree of central concentration and the "tidal radius" to define the cutoff of star densities at the cluster's edge.12

Because of this high concentration, the density near the centres of globular clusters is significantly higher than in the solar neighbourhood, reaching approximately two stars per cubic light-year.1