You're joking right? Consumers are pushing a desire for thinner lighter devices capable of longer and longer run-times with higher loads.
Believe it or not, consumers also like to not have to replace their device in 2 years because the battery only holds half the capacity it used to. Just because it's not on the box or part of the advertisement's spiel doesn't mean it's not something consumers care about. There are plenty of consumers who can see into the future beyond the length of their nose.
Something has to give when you are designing around these requirements. A lot of modern devices are thin because their batteries lack any kind of protection. Using flat lithium cells gives the designer far more flexibility to design a product rather than having a full battery pack with protective case and protection circuit.
You seem to be under the misconception that these rule each other out. Do you do much electronics repair? How many devices have you owned? Opened? Replaced the batteries on? I am on a tablet right now that is thinner than a Microsoft Surface Pro 2, but unlike the Surface it has a user-removable battery and doesn't sacrifice run-time to get it. My cell phone is thinner than an iPhone... and guess what? Removable battery.
Manufacturers aren't making non-removable batteries because of design constraints. They're making them non-removable because it ensures that when the battery wears out, the consumer is forced to buy a new model. Otherwise why permanently epoxy the battery into the device? I know all about unprotected lithium cells... I'm a certified Apple technician and have opened plenty of MacBooks. But you can have a battery that uses the case of the device to protect it without gluing the damn thing in so it can't even be serviced by someone with the proper training and tools.
The average consumer is likely to damage the types of batteries used in these devices and burn their house down in the process.
I'm well aware of this... it's made quite clear in our training and quite obvious when you're working on them daily. But it's not as necessary as you've been fooled to think. The "design constraints" and "users are demanding thinner" is just the bullshit lines they've come up with as an excuse to mask the actual reason: enforced obsolescence and increased revenue stream. If it were actually true, there would be no need for the epoxy, and no other manufacturers proving them wrong.
Given the pace of technology and the average use life of such devices, replaceable battery is one feature I really no longer care about.
That's nice. Not everyone is rolling in cash and prepared to buy a new phone or tablet every 2 years, especially when there's no technical reason to have to do so. Consumers have been conditioned to accept a worn-out battery as a legitimate reason to trash their otherwise perfectly functional and adequate device, which is insane and inexcusable. This would've never been accepted pre-iPhone/iPod. My sister's HTC One X is less than 2 years old and already can't hold a charge worth a damn. The phone is already 3 times the phone she needs, so why should she be forced to buy a new one? It's criminal. Luckily I am willing to replace it for her but HTC has made it unnecessarily difficult for no legitimate reason. There are thinner phones with user-replaceable batteries... they could've made it so she could do it herself, but that wasn't advantageous to their bottom line.
And if the batteries actually fail a quick and quite cheap trip to the repair shop will see it swapped out.
WHAT "repair shop"? Maybe for the lucky subset of people who live in cities near an Apple Store or some other electronics shop. But guess what? There's a lot more to the USA and world than the big cities. And the fact remains: there's no need for it to not be replaceable by the consumer. There's no need for them to pay $80 to have someone replace a $5 battery. And there's no reason to epoxy the batteries in so the repair shop can't even replace just the battery.
It's a scam, it's bullshit, it's anti-consumer, and it should be criminal. Unfortunately they've sufficiently brainwashed you so that you're inclined to parrot their same line which helps them spread the lie and make you an unpaid salesforce on their behalf, but those of us who have opened enough off these devices, and seen enough of what is possible, know the truth. It's too bad that the technically-informed are the minority of consumers, leaving the majority to be taken advantage of by the manufacturers, but unfortunately that's been the case for years.