What real-world factor often prevents a globular cluster from being a *perfectly* spherical shape?

Answer

Tidal forces from the host galaxy causing distortion over time.

Perfect sphericity is rare; tidal forces exerted by the host galaxy can act upon the cluster over eons, stretching or distorting its shape slightly, meaning the term implies near-spherical.

What real-world factor often prevents a globular cluster from being a *perfectly* spherical shape?
descriptionshapesphereglobularform