Because Jesus and St. Paul encouraged it?
"For there are eunuchs who were born that way, and there are eunuchs who have been made eunuchs by others--and there are those who choose to live like eunuchs for the sake of the kingdom of heaven. The one who can accept this should accept it." -Jesus
"To the unmarried and the widows I say that it is well for them to remain single as I am. But if they cannot exercise self-control, they should marry. For it is better to marry than to be aflame with passion" --St. Paul
"Now the Spirit expressly says that in later times some will depart from the faith by devoting themselves to deceitful spirits and teachings of demons, through the insincerity of liars whose consciences are seared, who forbid marriage and require abstinence from foods that God created to be received with thanksgiving by those who believe and know the truth."
You can read that passage in your preferred version as well -- http://biblehub.com/drb/1_timothy/4.htm -- it says the same thing.
Forbidding marriage among your leadership is, according to Scripture, demonic.
Just keeping it real.