It’s a good question. But first…
“The Root Chakra is the first chakra in the energy body, located at the base of the spine at the perineum, between the anus and the genitals. The Root Chakra location signifies its role as a link between the physical world and our internal energetic system”
Reading your question and the definition of the root chakra might already have given you a hint about what is going on. Basically there is nothing more physical than sex, its energy and expression. It roots you to the physical work first since sex is the source of physical creation of both living and non-living things. Making living things through pro-creation (babies) and making non-living things through creativity (inventions, discoveries, etc).
Harnessing that energy instead of “throwing” aka ejaculating it away helps you become productive and live an energetic and successful life in the physical realm.
This is why porn, masturbation, laziness, procrastination, etc are usually a sign of misuse of the sexual drive and energy. The drive you get from wanting to talk to women to seduce them (wanting to create babies) and being a go-getter in your purpose and work (wanting to create a legacy) is a very base and necessary thing.
Without it, one is not only detested by society but is ashamed of himself. Because he doesn’t provide any value to the world.
When one can control his own sexual energy, he is intelligent, focused, disciplined, charismatic, sexy, and powerful. All useful for the physical world we live in to make money, have sex, rise in status, provide for others, acquire power and build a solid foundation in the lower realm so that one can if he wants go higher.
Which is why sexual energy is also conserved by priests, shamans, yogis and various religious and spiritual orders in order to channel such power to their spirit. From the end of their body, up the spine and to the top of their head. Old wisdom encourages such sexual discipline not only to go up the ladder of earth but also, if one so desires, climb the stairway to heaven.