Provident Fund is a retiring benefit to an employee. This benefit is applicable until such time the employee ceases to be an employee in an organization. If an employee is continued after his retirement or reaches the age 58, 59, 60...still it warrants that this fund be contributed by the employer. The ILO has increased the retirement age and some countries are already following.
Further, the continuation of this contributions will be a motivation factor for other employees too! It brings out the importance that you have posted on the elders as well as in a situation where employees are thinking of changing employment every other day!