This is Habanero Cycles philosphy:
"Why not double butted and tapered tubing?
Double butted tubes are thicker at the ends, and thinner in the middle. This allows the builder to use tubes that would otherwise be too thin to weld reliably. This does reduce weight somewhat, but it also increases the flex in the thinner portions of the tubes, and makes the tube much more prone to dents. Besides, most bikes built with "butted tubing" have only one or two butted tubes (usually the seat tube and/or the down tube). Realistically, there are a lot better and more cost-effective ways to save weight on your bike than buying a butted frame (calculate the $/gram cost - you'll be amazed). Habanero frames are built from 0.9mm wall straight gauge tubing which is thick enough for reliable welding, prevents frame flex, and produces a very strong, yet lightweight frame.
Making a tube's outside diameter smaller makes it more flexible. Tapering a tube has the same effect. While there are those who would argue that a tapered tube makes a more beautiful frame, I take a "form follows function" approach. Massive 7/8" (22mm) straight chainstays and 5/8" (17mm) straight seatstays reduce rear end flex to almost non-existent levels. To me, that's beautiful!
Double butting and tapering of titanium tubing are both very difficult and expensive processes that add cost but little or no value to a bicycle frame..."
~ Men of steel need fibre ~