Actually, there is a set of incentives for professors to hand out PhDs. Before tenure, professors have to successfully graduate PhD students (or at least get mo

Actually, there is a set of incentives for professors to hand out PhDs. Before tenure, professors have to successfully graduate PhD students (or at least get most of the way there), otherwise questions will be raised in tenure review. After tenure, failure to graduate students equates to failure to attract new ones, loss of prestige, loss of connectivity to their academic network by way of a graduated student, etc.