At least you can install new batteries with different form factors now. Technically it would be trivial to just have a lid to install new ones.
Profit orientation is worse than customer orientation. It is also an ecological problem. Instead of changing batteries after 2-3 years, people buy new phones.
Lids ruin waterproof designs. Not so trivial.
Fortunately, they learned from that mistake and started to make iPhone batteries significantly more powerful. As a nice side effect, even a two-year old iPhone XR, for instance, still has excellent battery life today.
As far as I am concerned my phone never shut off randomly, I was perfectly fine with it. And yes indeed they made absolutely no effort to tell the customer that they could get the battery replaced for like a 10th of the price of a new phone, I don't believe for one second it was a communication error, and not a simple trick to get people to buy a new iPhone.