Then, sometime later, they begin to learn about other types of fly rods like bamboo & fiberglass. Between the two (cane & glass), fiberglass is much more accessible because of the price. They hear about the feel & sensitivity of fiberglass fly rods & how they compare to bamboo & become intrigued. This is why, for most folks, their first custom rod is often a fiberglass fly rod.
I've even heard fiberglass rods referred to as a "poor man's bamboo". I do NOT agree with this sentiment, as they are two different types of rods with different characteristics, but I understand the concept, particularly when you compare fiberglass to modern graphite fly rods.
Typically, once an angler fishes with a fiberglass fly rod, there's no going back. The feel of casting the line with a glass fly rod is one that can become addictive. More & more they find themselves picking up their glass rod & leaving the graphite rod at home.
Some of us (like me) who grew up fishing a fiberglass fly rod will often go back to them for sentimental & practical reasons. I still fish fiberglass rods myself & always will no matter how many bamboo rods I own.
For those of you new to fiberglass, they're not the slow buggy whips they used to be. They have a lightness in hand & yet retain the sensitivity & feel we love of fiberglass. There are limitations to fiberglass as it's used in fly rods - think line sizes & rod lengths - which is why you don't see many 9 ft 2wt fiberglass fly rods.
There's nothing like a good comparison & in the video below, Tim Rajeff does a great job of describing & showing us some of those differences. Check it out as it will describe the technical aspects quite well in a very clear way, showing you a side by side comparison of graphite & fiberglass fly rods.