I think the light line thing is combination of technology & marketing. They can do it so they do. Let's face it; fish haven't got a whole lot smarter in 40 years despite how many times we use "selective trout" as an excuse for getting skunked. If my grandpappy could catch them on a 7wt you can too. Remember the Orvis All Rounder? It's just that many of us have been brainwashed by the pencil lead gang and their marketers into believing we need these light line outfits for "technical fishing" what ever the heck that is.

Fishing is when I'm catching fish so I guess Technical Fishing is when I'm getting my butt kicked?

In the case of glass I think the glass rod makers also have adjusted to the wider market and offer light line outfits for the Super Selective Mensa Genus strain of trout that mutated directly from the Dufis Wet Fly Chasing strain immediately after "The Movie" was released.

Light lines and their relation to a delicate presentation has been WAY overstated IMHO. I fish Letort Spring Run regularly; a stream known for its finicky trout and I never fish anything lighter than a 5wt and fished nothing but a six weight for over 20 years. I chose those line weights because I can go from a midge to a weighted Sculpin pattern in heartbeat. I also was somewhat affected by a local famous angler who was my fly fishing hero who told me he used the same weight outfits there. I guess he knew his stuff because I have no trouble with my "heavy" line outfits there.

I do like to fish a long leader which helps; but even so, if you are casting over spooky fish; one or two line weights doesn't make ANY difference; the fish will bolt regardless. Case in point: I was fishing a BAITCASTER the other day in super clear water and fish were flipping out as my Senko sailed overhead tied to 17lb test Fluoro. They saw it BEFORE it even hit the water. What heck chance would you have with a -0000000 weight fly rod in those conditions?

I choose my line weights solely based on the wind and what rod length that will work best under the conditions I expect to encounter. If it's breezy and I plan to fish size 22-32 flies I grab a 4, 5 or 6 weight; if it isn't windy and I plan to fish size 22-32 flies I may grab a 3wt if I have one in the proper length. I could give a rat's arse what size line I choose for dinky flies; that's because it doesn't matter. I can fish a light tippet on any rod. I often wonder where this delicate flies; light lines thing came from. I fish Tricos almost every day and use everything from a 2wt to a 5wt depending on my mood and the results are exactly the same; I catch fish.

Getting back to glass; I admit I do own a few 3wt glass rods but there is a couple of reasons I chose those rods and line weights. In the case of two Retros I own, it was because that was the only line weight in that length available. Why Winston chose those line weights I don't know but I suspect it was because both rods are shorter and the impression today is short means light. In the case of my other 3wt glass rods which were custom built; it was because of the length & weight of the rods and the reels I chose to mate with them for balance.

The shortest and lightest rod in my quiver before glass & graphite was a 6'6" 4wt Orvis bamboo Flea. That rod balances well with several reels that easily hold a 4wt DT; my preferred taper. When I got into glass I started with a 7'0" 4wt which was fine with the same reels but soon I started with shorter glass rods from 5'0" to 6'0" and I wanted a smaller and lighter reel to balance better with their lighter weight. That forced me into 3wt territory because of reel capacity. Yea I know I could have said screw the balance thing and used a larger reel, cut my DT's in half or went with WF's but I didn't want to do that. Even though wind can be a factor with light lines; I use these short rods exclusively on small waters which in my case are usually rugged wooded streams where the wind is hardly a factor even on breezy days.

So I guess there is at least ONE good reason in my world to fish lighter than a 4wt.

Speaking of wind, sorry for the long post!