The reasons to why you should neuter your male cat are numerous. If your cat is an indoor cat and not neutered you will notice at about 5-8 months he will start to spray. He will spray everything from your doorway counter tops to your new big screen t.v. and custom made computer.
All the above will just cost you financially so if you have money to replace the t.v. and computer and hundreds more on specially made cat urine cleaner than you will be fine during the first stage of the indoor unneutered cats development. The second stage begins with a howell. This is aloud yodeling sound he will make calling for a female cat. This can get deafen and annoying and if you live in a location where you get fined for the barking dog prepare to be fined for the yodeling cat that woke your neighbor at 2:00 a.m. but if you have the funds and the sanity to deal with listening to this yodeling about 15 hours a day than you will survive the second stage.
The third stage starts at proximally 8 months to a year depending on when the spraying stage started. During this stage your sweet kitten who never gave even the slightest interest to the great outdoors will sneak out every chance it can to go in search for the female cat. At this time if you love your cat, which I know you do from putting up with it each time a new stage of its "growing into adult hood as an unneutered male" you've kept and loved and fed it and spent the money its cost you.
Nows the stage to worry. He's out some where on the "prow-el" with the female cat. Maybe shes a pet, or maybe shes a feral cat either way she isn't spayed, perhaps she belongs to a loving family like you who wouldn't think to let her get a sniffle without taking her to the vet, but don't believe in spaying. Then you could be lucky. If not maybe shes a feral or she doesn't have good owners. Her shots aren't up to date or maybe shes never had them then all of a sudden your pampered boy comes home with feline leukemia of FIV then you risk loosing the cat you love so much because you never had it neutered and it snuk out and got with a cat that has or is carrying a disease that is hard to treat and has low success rates.
With all that said you should have your boy neutered because it will prevent him from getting testicle cancer later and help prevent prostate cancer as well those are two great reasons alone.
So your cat is an outdoor guy is he? Your problems consist of the ones I mentioned above and some added on worries as well. The inside of your house might not smell and need constant cleaning but I guarantee you every corner of the outside of your house will. I also guarantee that every corner of your yard will. The spray might be so strong it could kill your grass or flowers.
Like the indoor cat he will go through the same three stages. The first stage doesn't disappear upon arrival of the next he just adds them on as does the indoor cat. I'm not sure if I made that known so I am now. Your outdoor guy doesn't have to wait for the door to open to escape. He's already out. You will start noticing him going maybe as little as a few hours to a few days maybe weeks or longer at a time. While he is going he is at risk. He is at risk of being ran over by an automobile injured or even killed by someone not wanting a strange spraying cat spraying their prize winning roses etc.
He is at risk of getting into fights with other male unneutered cats, and boy do they fight sometimes to the death! He could cause over population if he gets just 10 female pregnant at an average rate of 4 to five in a litter that is maybe fifty kittens in six to eight months after their arrival those females will be ready to mate. SO if half of the fifty were female thats maybe 125 more cats. Forever and so on and with this rate feral cats will over populate every inch of your neighborhood. He could be at greater risk of the indoor cat of bringing back feline leukemia and FIV, just because he's always out. Then he will come home if he lives that long. You will see the cat you cared for since it was a few weeks old so thin you can see its ribs. He will be all cut up from fights and he could've contacted a disease from a cat he was with. You pick him up and rush him to the vet. Maybe surgery is required at the least stitches and antibiotics. And you take him home and start fating him back up.
Great if you got him neutered if not as soon as hes feeling well enough off he will go again. If this is not enough to convince you to neuter your cat I'm not sure what else will. Remember neutered cats will not get testicle cancer and it will help prevent them from getting prostate cancer. Being neutered wont make your cat mean it actually makes them more docile. It wont hurt their feelings to be neutered especially if you do it pre-spraying stage. It won't hurt them it will keep them home safe with you. It wont make them overly fat like on t.v. they may gain a few extra pounds but nothing serious. I'll leave you with this thought an unneutered house cat lives an average of 2-3 years, an unneutered outdoor male lives an average 8 months to 18 months. A neutered male lives an average of 12-18 years depending on his living environment do yourself a favor neuter your cat so he can live the longest life possible with you.