Why is it a hurdle for a man to be 36?

Youth is capital. Whether men or women are in their teens or twenties, they are invincible in youth, spirit and time. After the age of 30, after all, I have a family, and my family responsibilities are great, and my energy is not as good as before. Moreover, some industries have youth to eat, and at the age of 36, I may be eliminated by some industries. If a man doesn't have a certain occupation or a certain technical level at this time. Will face the pressure of being eliminated.