Here's something I've noticed. All but one of my bikes have steel frames. All have been exposed to varying levels of rain, mud, road salt, and so forth. None of them have ever been pampered. Over the decades, none of my frames have seen serious rusting with one exception. The paint that they put on frames is pretty darn good. As others have mentioned, the insides of the tubes can be coated with something resembling varnish. The things that have rusted have tended to be fasteners, drivetrain parts, cables, etc. So I wouldn't go out of my way to seek out special frame materials.
Now the exception was a bike that was half buried in my college housemate's family's barn for possibly decades, an ancient Hercules. And its frame was badly rusted. So I think long term storage in wet or corrosive conditions can definitely rust a frame. Salt air, sure. The pics we've seen of frame rusting on this forum must be due to more than just normal use in normal weather.