Vets push it because most American's are not responsible owners and can't keep their pets from "accidentally" reproducing. From what I have seen and read, a male dog will not develop fully if he doesn't have the hormones that are needed. He may look less masculine, leggy, not as thick, etc. My breeder who is also a vet recommends not neutering till at lease 14 months (maybe longer, can't remember). I will wait till he is 2 or older, or never, not sure....haven't decided. I also found out that neutering at a young age can have bone development issues...arthritis, etc.
For me, since I don't let me dog out of my sight, he is never out with out me being out with him, I feel I can avoid neutering without worrying about him knocking up someone.