While protective cases make the phones marginally thicker they don't make them less water proof. Which is in my opinion the purpose of making phones sealed and as port-free as possible.
And even with the protective case my current phone is much thinner than any phone I had with a user replaceable battery.
BTW, Samsung Galaxy S5 had all those features, even replaceable battery and was still waterproof.
Like forever, some of the smartest people around admitted that they did not know. They created the entire field of market research. Today I think that is dead. In the past decade we moved to an entirely different model of force-fed consumerism, which is driven, as you say, entirely by the supply side. Oddly the near communist era uniformity we see goes against our stated beliefs in data-driven, targeted markets.
A whole other layer is how we increasingly project our own desires onto others and assume they must be crazy not to want the exact same thing as ourselves. Where does that come from? Here on HN I get tired of hearing these very strident, cock-sure remarks about "what people want is...". Let's just admit we don't have much idea about what other people want. There's nowt as queer as folk. And some of the most interesting markets may in fact be marginal. Smaller markets do not mean unprofitable ones.
I definitely do, to some extent. More sealed is good, I don't want water and dust inside my phone. The thinner the phone the thicker and more protective the case you can apply before it gets too thick. Or you could stick a battery in the case, or a USB hub, SD reader, etc. What stops this case from existing right now?
> It's going into a protective case anyway.
With that in mind, it seems it's not really customers that want ever thinner, ever more sealed and port-free phones. The very first purchase they make after buying a new phone already defeats the purported benefits of those design choices.
I maintain this market is supplier-driven, and customer preferences have near-zero bearing on how phones look like today.