Regarding aluminum steerer tubes on suspension-fork-equipped mountain bikes: if a consumer were to purchase a new mountain bike in 2014, with the bike retailing for maybe a little more than a thousand bucks, the bike would very likely have an aluminum steerer tube on the suspension fork. If a consumer were to purchase a new mountain bike in 2014, with the bike retailing for something like $5000, that bike would also very likely have an aluminum steerer tube on the suspension fork. 1 1/8" steel threadless steerer tubes on suspension forks are still common on inexpensive bikes. Carbon fiber is also sometimes used on very expensive, lightweight supsension forks' steerer tubes.
On decent suspension forks, aluminum is by far the most common material used for steerer tubes, and this is absolutely nothing new at all, pretty much covering the entire 1 1/8" threadless era of mountain bike forks. Steel was the material of choice in most cases during the 1" and 1 1/8" threaded era, which was a fairly brief time span in the realm of suspension forks on mountain bikes.
Last edited by well biked; 11-24-14 at 02:24 PM.