You would be surprised to find out the answer and it has nothing to do with their religion per se. It hasn't been that long that they chose to do this or be thins way either. It started in the 10th Century when they did get married before, but they also had condubines too and had lots of children. It was when taxes came around and some of those children were ti get inheritences. "The idea of Catholic celibacy is especially foolish when you realize the reason behind it. Before the middle ages it was allowable for Catholic priests to have multiple wives and mistresses (concubines). But with concerns for protecting Church property from inheritance Pope Pelagius I made new priests agree offspring could not inherit Church property. Pope Gregory then declared all sons of priests illegitimate (only sons since lowly daughters could not inherit anyway in society)." I cannot do justice with all the information on that site. I certainly do hope this site stays up a lot longer than it did a while ago when I could not find it. Many of the links within the site do not work anymore or have been moved. The History of Catholic Celibacy