Because over the years, there have been changes.
Evolution is a process of historical development of the organic world. The essence of this process consists in the continuous adaptation of living things to diverse and constantly changing environmental conditions, in the increasing complexity of the organization of living beings over time. In the course of evolution, some species are transformed into others.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.