If you have an intact male or female cat, you will certainly know that it is not a pleasant experience. Intact cats guard their territory and status zealously. Their sex hormones power their urge to roam and fight (especially intact male cats). They can disappear for days, especially during the mating season, and may come back home with fight wounds and abscesses. These cats are also likely to get feline immunodeficiency virus (FIV) or feline leukemia virus (FLV) when they get into contact with other cats outdoors.
Intact male cats have greater risks of developing prostate problems and testicular cancer. On the other hand, intact females are more predisposed to mammary and uterine cancers, as well as uterine infections. Intact females will also fight other females.
As you can see, having an intact cat is a recipe for frequent and expensive veterinary visits. Having your pet spayed (female) or neutered (male) is the best decision you can make to protect your pet from the aforementioned risks.