Look at the rifles of the past
Virtually without exception they come with iron sights. By the 50s you could get varmint models that didn't have sights, only drilled and tapped for scope bases. By the 70s, it was about half and half, some models came with sights, some didn't. Today, rifle makers just generally assume that rifles in certain classes of calibers are going to be scoped, so putting sights on them is just a waste of money. Other calibers are still sighted as the standard, big bore rifles, for one.
Scopes can and do fail, and accidents also happen. To me, a set of sights on a game rifle is just something that ought to be there. Even if you can't drill tacks at 500 yards with the irons, you can still nail a deer/elk etc, at a distance.
Considering the expense and the time of a big game hunt, isn't having sights you can use if your scope gets broke worth the trouble? It is to me.