I have a very good old bike. I don't think my budget allows spending for an equivalent new bike. If my budget allowed the spending, I don't have space for a 2nd bike. Further, the production bikes I can ride around here would not fit me as well as my current bike does.
I could, perhaps, find a used bike at a low price. I'd rather ride than shop. Hell, I'd rather do almost anything than shop.
If you don't understand why some people rid old steel bikes, do you ever realize that as soon as you roll your new bike out of the store, it's old, no matter what materials are used in making it?