Many ranges have gotten fed up with the steel and aluminum brass because it is such a nuisance to separate as recyclable metal. They really prefer that brass be used. I know of a few ranges that only permit brass cases.
For indoor ranges it makes great sense to limit the cases to brass because it is an efficient recycling system. The cases fire, drop on the floor, and are collected for recycling.
Aluminum cases must be separated manually. Running a magnet through the collected brass is a nuisance, and not entirely reliable. Hornady, for example, has experimented with many techniques for separating cases, and the only reliable method they have found is "two Asian women and a big table".