Unlike transgender people, nullos do not remove their genitals because they suffer from gender dysphoria. They see castration as a positive step which is not about removing something they dislike but about moving towards something more desirable.
For example, some nullos feel their genitals are uncomfortable. They do not like they way they can be squashed while sitting or harmed during sports. Sometimes medical conditions or injuries can make erections painful. While numbing the organ can solve this problem, it can make detecting infections difficult. So men may opt to have their genitals removed to avoid future complications. Other people may decide to become nullos because they are embarrassed or uncomfortable about the size or appearance of their genitals.
Nullos can still ejaculate, although they do not produce sperm as men with their genitals do. They cannot get erections, but they can still experience sexual pleasure, particularly through taking a submissive role during anal sex with another man.
As castration is an unusual and extreme act, nullos are subject to rigorous psychological testing before medical professionals will remove their genitals. People should never attempt to remove their own genitals to become a nullo. A medical procedure is the best way to ensure the genitals are removed safely in a sterile environment that minimizes the risk of infections.
Nullos should take testosterone after getting their testicles removed. This helps offset the drop in testosterone made naturally by the testes, minimizing the risk that a nullo will develop depression. There are few other side effects.