Whither the DT fly line?
In trying to replace a few older fly lines, I have discovered that many of the major brands of fly lines now have eliminated the double taper fly line from their high end floating lines. For example, Scientific Anglers does not make a GPX double taper, and RIO does not make a Gold or Grand double taper. I wonder if this is for marketing reasons (i.e., can't reverse a WF line so you have to replace the line twice as often) or for some other reason. I personally prefer a DT for several reasons:
1. Permits longer roll casts than a WF with its shorter belly
2. In making longer casts (longer than the WF belly) I don't have lighter running line trying to turn over the heavier belly
3. The aforementioned economy of reversing a DT when the tip wears out.
Do others share my regret about the diminishing availability of the DT?
After spending a considerable amount of time online, I located a few older GPX DT lines to purchase, but I fear that next time I need to replace lines, there will be none to be found.