Now this is local civilization. Emerged from the soil of this land. How many of us abide by the designated duties?
Teens are ever increasingly indulged in addiction and sex.
Grihastha are most selfish and devoid of performing duties towards society.
Vanprastha is not able to leave everything aside.
There hardly few who can reach to the age of 75 :).
All 4 stages of life and their duties are designed as per general tendency of human body and mind at that age.
Grihastha and Sanyasi are on front stage, actively performing duties.
Brahmcharya and Vanprastha are on training. Preparing self for front stage active participation in material and spiritual progress of the self and society.
If not 100%, when you try to abide life with this, you are bound to receive आनन्द & सुख.