Both of my boys were neutered when I got them.
My childhood dogs, all male, were neutered for multiple reasons. Birth control, behavior modification (kind of, I think my parents thought that intact males just automatically mark everything etc) and, as others have said, because it's just what you do.
Future males that aren't show dogs will likely remain intact at least until full maturity and maybe indefinitely. Females I'm not quite so sure about. Pyometra scares me, and although I know it's not super super common, I've read that it occurs more in females that have never been bred. But definitely until full maturity as well.