Of course many do not keep that vow.
I found out several years ago that the priest who married my wife and I was forced to leave the priesthood. His huge crime: He fell in a love with a woman.
So sad, he truly loved the Church and serving as a priest.
Holy matrimony and holy orders need not be mutually exclusive.
It’s not that simple... and the problem can be seen by changing just a few words in the example:
“I found out several years ago that the marriage counselor who helped my wife and I was forced to leave the profession. His huge crime: He fell in a love with another woman.”
A priest—who has taken the Church as his Bride—has no more business “falling in love” with another woman than I do (I’m married to a lovely woman, myself). He has a grave moral obligation to guard his heart; and those who were charged with his priestly formation had the grave responsibility of training him in ways to guard his heart thusly.
Jesus Himself encouraged celibacy for the sake of the Kingdom (cf. Matthew 19:10-12). St. Paul said that celibacy was the preferred state for those who minister (cf. 1 Corinthians 7:1-7). St Paul goes so far as to say the following:
“I want you to be free from anxieties. The unmarried man is anxious about the affairs of the Lord, how to please the Lord; but the married man is anxious about worldly affairs, how to please his wife, and his interests are divided.” (1 Cor 7:32-34)
There’s often a sort of sentimental “offense on someone else’s behalf” in cases like this—akin to the idea of “Well... I’m free to have sex and intimate companionship with my spouse, and it doesn’t seem right to deprive someone else of that, so let’s get rid of the celibacy requirement for Latin Catholic priests!” That’s soft-hearted... but it’s short-sighted, too. Priests who are married have a divide in their lives which others don’t have with secular careers—or even with Protestant ministries. There are decisions which no man should be forced to make (e.g. if your 5-year-old daughter is dying across town, and a fallen-away parishioner is dying in front of you, do you give the last Sacraments to the dying man/woman who may be in a state of mortal sin, or do you leave him/her in order to be at the bedside of your daughter?). Should he abandon a soul to a serious risk of damnation, simply out of a desire to be at the deathbed of a daughter who’s in a state of grace?
Moreover, some of the strongest advocates for the celibacy requirement are *married priests!* They, of all people, have lived with the state of being torn in contrary directions—short-changing their wives and families in order to dispense the Sacraments, etc. Fr. Dwight Longnecker (a married Anglican priest who converted to the Catholic Church) comes to mind, in that regard.