I do not have much to add to what already has been said in these last comments, which is more or less the two keywords from my article: Conservatism and commercialism. Most people getting interested in backpacking for the first time are probably a bit afraid of this unknown world that is tempting them. They want to be safe. They want good solid stuff. It is a bit difficult for sales staff to convince them that a lightweight pack is good enough for their needs (some of my interviewees have worked in outdoor retail). Particularly if the heavy packs are more numerous, have been around for a long time and offer better commission to the sales staff. This is where commercialism comes into play. “People buy what stores sell” as Chris Townsend formulated his reply.
I have had a representative for a major retail chain over here, when being offered to sell my book Smarter Backpacking say: “We are not that interested in lightweight backpacking, because we think it might diminish our sales”.
There is also the questions of different approaches to backpacking, which also have been touched upon by some of you in the comments. I think what Andrew Skurka calls “hikers” and “campers” sums it up. Walking short distances and staying around camp makes weight less of an issue.
My personal mission in lightweigh backpacking derives from the fact that I see way too many people carrying lots bigger loads than what is necessary. And particularly women, older people, kids and parents. In this group you find people that do not have the physical capacity of a trained athlete. Parents with small kids do have to carry double until the kids are big enough to carry their own gear. I want to make all these people aware that there are options to what is heavily advertised by the established multi-nationals. In order to vote with their feet, with their dollars, they have to know the breadth of options. That it is not only a questions of choosing between three packs, all of which weigh 5 pounds, give or take a few ounces, the difference being the color, fabric, size of pockets or number of zippers.
There is a favorite marketing acronym of mine (I have been doing market research most of my professional life) that is called AIDA. Most of you probably know that one. What this means is that a product/line of products have to be brought to your Attention before you can develop an Interest in it. This might escalate to a Desire for the product, that could eventually lead to the Action of buying it.
Ultralight and lightweight backpacking has still not come to the attention of large groups of backpackers. And when it does it faces conservatism and commercialism. Like almost everything new in this world. However, I am optimistic. Carrying light is simply too good an idea and brings too much comfort for it to be stopped. A colleague of mine used to say: “Nothing can stop an idea whose time has come”.
Which is not the same as saying that everybody will go ultralight.