Because your purifying yourself physically and energetically and removing energetic blockages your sexual energy is becoming more pure and is able to raise to higher energy centers instead of being stuck in your lower energy centers responsible for survivability, fear, lust etc. At its core most NSFW content is low frequency energy and is “disgusting”. It induces and feeds off Lust, hedonism, vanity and infrasexuality. Higher sexuality/ Suprasexuality is conserving, cultivating, raising and circulating sexual energy through transmutation practices or with a loving partner and not wasting and shooting it out your bell end after 10 mins but instead circulating it and transmuting it. If your transmuting the energy properly, semen retention is the most beneficial practice that you can do to benefit your health and life in all aspects and will greatly accelerate spiritual evolution