There are two points here that really should be addressed.
First, is the complaint of "elitism." Again, as I mentioned above, that claim is not a response to the concept of lightweight backpacking. It's simply an attack on the people promoting the concept and therefore has not value in this debate. If a person is "elitist" and they think they're better for XYZ reason, that just makes them a crappy person, but it doesn't change the argument. In addition, from my experiences, I have seen no evidence that elitism is any more prevalent in the lightweight backpacking community than the traditional backpacking community. Also, since the trad backpacking community is much larger, for every one elitist is the UL community, there are most likely 10 elitists that say: "I have this bomber [fill in the blank], without which you have no business being on this mountain."
Which leads to the second point: OF COURSE the possible range of conditions that you face must dictate the gear that you bring on a particular trip. If you need a high level of wind or snow protection a 4-season tent may be a requirement. You can't judge the UL weights in a New England summer against a trip to Nepal. Different conditions call for different gear, BUT that doesn't mean that weight shouldn't be considered just because a person is doing a trip in a harsh environment.
For example, if my memory serves me correctly, the famous American mountaineer Ed Viesturs writes about going fast and light when he climbs. I believe there's an interview where he talks about carrying a 45-pack on a 4-day unsupported, alpine-style summit attempt. Also, in his book he mentioned he carries a 0 degree bag (maybe it was a quilt) on his climbs and then uses his clothing when he sleeps. If a super athlete climbing Everest and K2 still bothers to consider weight and can maintain a 45lb pack weight, I don't think it's a bad idea for us mere mortals to consider pack weight too.
There's only one reason why this issue is really something that I care about at all. I remember starting out backpacking in college and spending gobs of money and carrying a sizable pack. Going out in the woods with friends was great, but the backpacking part was a pain – figuratively and literally. I remember what that was like and how over time I realized on my own that I didn't need a cup a bowl and a plate. I realized that I didn't need to buy expensive water bottle and could just use cheap, free bottles. Now, when I see 18yo college students who were doing the same things I was doing, I wonder why in the age of the internet that these ideas haven't gotten to them yet and what can be done to help them travel safely and comfortably, and spend less and be more creative.
I don't think that's a bad or elitist why to think, it seems like a caring way to think. I'm learning every day from people on this forum and in the field. And, if anybody asks, I'm happy to show them what I do and why I do it. I think one of the coolest things about UL philosophy is that we can be creative and that there ISN't one right way to backpack.
If being exposed to UL or ANY other ideas makes a person feel bad and defensive, then that's their own shortcoming. When I teach people as part of my job, I LOVE being questioned, because it shows that the audience is listening and it forces me to consider and explain the subject that we're covering.
Now, I'd like to be able to get back on the topic of examining why UL backpacking hasn't spread more widely. Although, I must say that defensiveness and resistance to new ideas may be a big part of explanation.