Or he may have become a widower at an early age. We are not told. The Jewish custom was to marry at an early age, and as Paul said all the apostles were married, and he too had the right to be married (or re-married if he so chose). Since Paul was constantly on the move, he preferred to remain single. But he called forced celibacy (as in the Catholic church) a doctrine of devils. Even unforced celibacy is an exception to the rule, as Christ made it perfectly clear.
The fundamental reason is found in Genesis 2:18. "It is not good that the man should be alone. I will make him an help [a helper and companion] meet [suitable] for him". Husbands and wives are to complement and complete each other. At the same time the husband is "the head" of the wife, just as God the Father is "the Head" of Christ, and Christ is "the Head" of the man (1 Cor 11:3). Hence Christian women must also cover their heads and hair during worship. That veil is a symbol of authority ("power" = exousia) because of the angels. And Christian men must keep their heads uncovered.
