I'm not sure why there are so few steel HT frames on the market. I think it's because most folks buying a HT are probably new riders buying in the $500ish price range and they've been programmed to think Aluminum is better because it's lighter (and having never riden before they don't know what to look for in a frame). I don't ride a HT but if I were getting one I'd have a preference for steel over AL.

Do you have components already and that's why you're looking at frames?