It reduces the need (hormones) to reproduce in dogs to a certain degree. Of course, they will still go around and hump things. Imagine you being horny all the t

It reduces the need (hormones) to reproduce in dogs to a certain degree. Of course, they will still go around and hump things. Imagine you being horny all the time and you can't do anything about it. So neutering helps against this. If I remember correctly, it also reduces the risk of some type of cancer plus the risk of unwanted puppies. The link between agression and neutering has been refuted by some studies.