When you come down to it is steel really that much heavier than AL? Maybe a pound in a frame. CF maybe several ponds. But I'm not really seeing AL having that much of a weight advantage.
Depends on the frame. I had a steel frame that was 6.5 pounds. Rode awesome but heavy. My current aluminum bike frame is just a tiny bit over 4 pounds. So that's a 2+ pound difference. Whether it matters to you is one thing...but there can be quite a difference. For some 2+ pounds is a huge deal. I weigh too much for it to really matter much.