I feel like you might underestimate the absolutely insane amount of market research a company like Samsung does for their products. The tech oriented consumers are going to be way more vocal about features they do or don't want versus the general masses. I demand a removable battery in my phone, but most consumers either don't care or don't even think to make the distinction.
Shiny and sleek devices sell. The edge screens seem somewhat gimmicky but they sure do look good and compete with Apple for consumers after that kind of device. I think Samsung overall makes excellent products but for my tinkering and interest in technology they're not my kind of product.
I agree in that features that might be important to me, may not be important to a lot of people. I may be underestimating, but you may also be overestimating the amount of research they do, especially considering they sold a phone not once, but twice that caught on fire.
Then there is also a question of market research versus companies doing what they want in order to maximise their profits and force people to upgrade and spend more money. Do you seriously thing a company like Apple who would possibly do more market research than Samsung, do you think they researched what consumers wanted and then decided to remove the headphone jack, or perhaps a way to force you into buying their own hardware because of their proprietary lightning connector.
LG have a metal back, besides the plastic back doesn't bother me in the slightest, as I have always used a case on any phone I have bought. I would say from what I have observed that the majority of people also use a case.