Re: Why fibreglass?
I think the allure of fiberglass is that it is tougher, smoother, and different.
I see alot of similarity between the resurgence of fiberglass fly rods and steel framed bikes. (dominant frame material for high-end bikes has more recently been carbon as well, and aluminum prior to that) Carbon (aka graphite) is indisputably the best material if you want to build as light a bike/rod as possible for a given strength need. But steel/fiberglass offers a different feel that some people prefer over the lightest thing out there.
Do not confuse this as an endorsement of steel fly rods, I wouldn't wish those on anybody.