Due to the difference between pay and unemployment benefits, the employee still has less money at the date when they would have resigned and they may have been counting on that money to see them through the job search.
During the two months after they gave notice, the employee might have intended to send out applications in the evenings. Since there is often a significant lead time between submitting an application and hearing back, the employee may have been counting on the two months of employment to burn some of that wait.
Hiring is probably also cyclic. For example, between Thanksgiving and New Years is probably not a very productive time to be looking for jobs. The employee may have been counting on the two months before their resignation date to get them through one of these slow periods.