Because they are of a different polarity, which is needed in 3D/4D (light needs dark, fire needs air, dualism).

The next age is whatever it is in the Zodiac, I don't remember. But we are leaving Pisces, which was always known as an age of naivety and optimistic/blind servitude to rulers. Zodiacs are more important than you realize, it's the foundation of every religion and secret order. Even The Bible. Astrotheology.

This is all in every super ancient religion/cult, and even in buddhism, hinduism, f.masonry, bible, egypt, greece (especially Greece and Egypt!), rome etc.

The universe is electric and the position of the stars and planets affects our behavior and moods. Said moods become massive when billions of living beings get affected.