DT lines offer the same basic taper they did 40 years ago, while the WF lines have evolved to optimize casting distance, presentation, fly weight and bulk, wind conditions, etc, etc.

So is it any wonder they outsell the DT lines by such a large margin, and is it a surprise the line makers have concentrated on producing what's selling, and that fly shops stock the more popular lines? I realize that doesn't solve your problem, but it's a fact of life. If roll casting (and long-imbedded preferences) is the only thing keeping DT lines around, I wouldn't hold out much hope for a revival. Maybe one of the newer WF head designs would roll cast well?