In spite of what a lot of people like to tell you, scopes are just better for most people, and there is certainly nothing more ethical about killing a deer with iron sights instead of a scope.
The great majority of hunters aren't really "shooters". They take ole betsy down to the range the week before hunting season, hit the target with a few rounds and they are ready.
For those that shoot a lot, well, scopes are still better. I only hunt regularly with one rifle unscoped, an 1891 Argentine Mauser with a peep sight. I can get reasonably good groups with it at 100 yards, but even at 150 they go all to pieces. I simply cannot see as well with peeps, or irons, as with a scope.
When hunting very early, very late, or in the middle of the night I find scopes a huge improvement over any kind of iron sights. I'm sure some of you think hunting at night isn't ethical, but we love to go pig hunting in the middle of the night.
And at the end of the day it's all about market forces. Ruger, Browning etc. don't force us to buy anything, they just try to make what people will want to buy. And apparantly the vast majority of people want rifles with scopes.
There are rifles available with iron sights, you may have to order it because you are the only person in town that wants one, everyone else wants a scope so that's what dealers have in stock.
Personally I think only gun snobs wouldn't hunt with a scope.