Fishing rods are tools. I don't believe they need to be protected. A well used tool can still last a lifetime if it is scratched and damaged. Its function will not be affected by appearance.
I'm not saying that its totally stupid to use a rod tube, but I recommend not doing so to protect just from scratches and nicks… chances are that's going to happen anyway while you fish.
The butt sections of these rods are extremely durable and strong. It takes a special kind of pressure at a very specific angle to really break through the lower sections. This kind of damage is hard to do. I've only done it once when I fell right on top of the section directly above the handle.
I just strap my rods to the side of my pack with the butt of the rod in the water bottle pocket while hiking, and the rest behind lashing straps or the side compression straps if they aren't totally used for compression of the pack. I leave them in their rod sock/fabric protector to help from minor scratches, from, say, branches as you walk the trail.
I have never broken a rod from carrying it, only from being stupid or falling while fishing with it in my hands.
I don't think there's any harm to the weight of a rod tube, but I'm just offering the idea of minimalism and that it isn't even necessary.
The major benefits of Tenkara rods are that you can replace one piece of the telescoping rod. It isn't that expensive. I've had to replace sections on many rods in the past when I've broken them in other ways. Its easy. I find its so easy that I just don't bother with rod tubes.
On any given day that I'm not backpacking, I'm carrying the rods strapped to my zimmerbuilt guide sling anyway… never use rod tubes accept when trying to carry many at once in one tube, for the sake of carrying extra rods, not protecting them :)
Meanwhile, the boxes these rods come in act as perfectly good rod tubes. They are light, they are easy to open and close, and you can reuse the plastic instead of throwing it out. Sweet.