If a university has a strong endowment, it provides assurance that the operating budget will be buffered against economic downturns. If universities did away with endowments (and did not replace them with mind-boggling amounts of insurance), it would increase the chance that professors' jobs and/or salaries would be at risk. Unlike most jobs, academic positions can last for half a century, so it is reasonable to look far into the future when assessing the desirability of a particular position.