ANSWER:  It is not that you HAVE TO neuter him, they just make a better pet that's all. Plus neutered males of course do not get Testicular Tumors (often malignant). 
 

(1)   Neutered males bite people less than un-neutered.

(2)   Neutered males do not mark their territory as much as un-neutered.

(3)   Neutered males fight less when meeting other male dogs in the park or visiting with other males.

(4)   Neutered males do not try to get out of the yard like an un-neutered one if a female dog in heat comes around.

(5)   Neutered males that escape the yard by accident wander less and return home more often unscathed than an un-neutered one who gets loose.

(6)   Neutered males are often more content, thus making a more loving pet.

(7)   In many locations, the yearly license fee for a dog is less than one that has not been altered.

At two years of age, expect at least 60 days to see total improvement in all aspects mentioned above, as Testosterone is stored in the dogs muscle tissue and internal organs as well.