Why were some early Muslim ascetics called “those who always weep”?

Early Muslim ascetics were referred to as "those who always weep" because of their practice of constantly meditating on the passages in the Qur'an that describe Doomsday.1

This group emerged during the early Umayyad period as a pious reaction against the growing worldliness and luxury of the time. In addition to their focus on the afterlife, these ascetics viewed the world as "a hut of sorrows" and were characterized by their strict adherence to religious injunctions, frequent acts of piety, and a particular dedication to night prayers.12