The fly rod industry today is focused & obsessed more with rod weight than ever before. Many rod companies are spending a lot of their resources in doing everything they can to make their rods weigh less than before. Every year it seems rods are getting lighter. Some companies proudly advertise this, which is fine, so long as they haven't compromised other aspects of the rod in order to get there. Often though, I find they have. The question of why one wants a lighter rod is often never asked. Is it for reduced wind resistance? For less fatigue to the angler's arms & wrist? Is it because a lighter rod casts better than a heavier one?
When designing a rod you've got to consider the rod's "ease of use". How will this rod feel in the hand? Never mind how much it weighs, how comfortable will it be to cast & fish? The over-all weight of the rod is not the main point of focus when you look at it this way. What does become important is how well the rod is balanced, or in other words, how heavy the tip end of the rod feels when holding the rod level. Its this outboard weight (everything beyond the grip) that's most important & will be the deciding factor in how quickly it will fatigue the person casting it - regardless of the rod's overall weight.
Extra weight in a fly rod is not always a bad thing anyway - especially for some rods & rod actions. That "extra" weight can sometimes be the key to sweet, smooth rod action. Ever hear someone describing a rod & say something like "this rod practically casts itself", or "the rod does all the work"? Well, that's because the rod was designed in such a way that its weight would be distributed in just the right places along the rod. In a well designed, yet heavier, rod you'll never notice the "extra weight".
So why do a lot of rod companies spend so much effort telling you how little their rods weigh? My guess is because they need a trend. You see, trends & fashions sell things & they need you to come back & buy another rod from them after your current one goes out of style. To me this is silly & it's why I put so much of my focus into how the rod performs. I'm always asking how a rod will cast; how will it feel in your hand; is it a rod you could easily fish with all day? If I can answer these questions with a "yes" than I'm happy because, to me, all of that is more important than the overall weight of the rod.