The following is a quote from Bill McMillan in the preface to Jock Scott's "Greased Line Fishing for Salmon and Steelhead". I think Bill nailed it...
"There was, and still is, considerable confusion as to what synthetics, technologies and ethics should be included in the whole of a long and dignified fly fishing tradition. With the rapid advances in tackle technology it was easy to lose sight of tradition, and yet if fly fishing was to remain an historical whole, anglers were going to have to accept self imposed restrictions on their effectiveness. Still there must always be room for invention, and the difficult task of the fly fisherman of the 1950's, which continues even today, is to find and perhaps even define a balance between tradition and invention.
The invention of the dacron sinking line in the mid 1950's allowed anglers to pursue fly fishing into the depths of rivers and lakes. Fly fisherman could immediately explore a whole new set of mysteries that had been entirely unavailable to the preceeding ages of fly fisherman simply through advances in line technology - not through any advance in either thought or skill. It was both exciting and a little disturbing if one put it to any prolonged thought. Was technology to replace the mental invention and skills the preceeding 500 years of fly fishing had been based on? This leap was so great in magnitude and so sudden! Curiosity overrode objections, and steelhead fisherman, especially, leapt headlong into a 20 year preoccupation toward fishing almost exclusively with sinking lines, solidly re-establishing the old myth that steelhead are bottom bound and refuse to rise. It was an especially unhealthy myth in that the steelhead himself was greatly misunderstood, and this great fish's reputation lessened some in comparison with the Atlantic Salmon.
Eventually even the sinking line wasn't enough and a few anglers went as far as split shot, sometimes using as many as 5 cannonballs (a full ounce of weight) and with that a total schism from the traditions of fly fishing. Anglers hundreds of years before could have easily resorted to such devices if they had dared to defy the grace of casting inherent to fly fishing tradition. The pursuit of bottom fishing with a fly rod had seemingly reached its limits."