The general belief about having children is likely that anyone can do so. Most if not all of us tend to presume that producing offspring is something inherent to all human beings once they've reached a certain age. In fact, most procreation efforts probably involve preventing pregnancy from taking place. There are however people who want to and have attempted to conceive a child but have been unable to do so. A person who is unable to produce offspring is sometimes referred to as being infertile.
Contrary to what some males may believe, male infertility can and does occur. The notion of a male being infertile can be a significant emotional blow, as it contradicts old stereotypes of men as being sexually vigorous and fit. The inability of a male to produce offspring may be viewed as a failure on the male's part to live up to expectations. The term impotent for example typically refers to males, not females, who are unable to conceive children because of a sexual dysfunction. At its root, the word impotent refers to one who lacks potency, or strength. An impotent man then may literally be considered a man who lacks strength. Most men would likely consider it an insult for someone to refer to them as being weak.
There are various causes of male infertility, but typically male infertility comes down to one of two causes: an inability to perform sexual intercourse, or nonfunctional semen. The performance of sexual intercourse, thought not absolutely vital, is the typical means for producing offspring. The inability of a couple to have intercourse then is clearly going to mean difficulty conceiving children. While women can have difficulty with intercourse, they may still be sexually functional. A male who isn't functional sexually will find it highly difficult, if not impossible, to have intercourse under any means.
Men may believe they will always have semen that's capable of fertilization, but semen can be and is sometimes damaged to the point of losing its ability to fertilize. There are any number of ways that a man's semen can lose its capacity to fertilize. Having a vasectomy, a sterilization surgery, would be one obvious way. Physical trauma to the testicles can also damage semen output, as can excessive heat in the area of the testicles. Studies suggest that smoking cigarettes can also damage semen and potentially make a male infertile.
While the reasons for male infertility can and do vary, infertility solutions for both men and women do exist. The issue of infertility is broad enough that there are medical facilities that treat infertility and nothing else. There are infertile men who don't consider their infertility to be an issue. Those men who are infertile and do consider it a problem have treatment options available, and should seek them out.