If you don't want to breed and have not bought a show-quality kitten you should spay or neuter your kitten.

Because:

• You don't want to add to the cat overpopulated world
• You can eliminate marking and roaming behavior
• You won't experience getting upset because your cat roams to much, urinates outside the box, peeing in your shoes etc. calling and rolling around when females close by goe into heat.
• You can decrease your female cat's chances of developing uterin cancer and  eliminate any risk for testicular cancer in your male cat.